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2019-07-12mm/swap_state.c: simplify total_swapcache_pages() with get_swap_device()Huang Ying
total_swapcache_pages() may race with swapper_spaces[] allocation and freeing. Previously, this is protected with a swapper_spaces[] specific RCU mechanism. To simplify the logic/code complexity, it is replaced with get/put_swap_device(). The code line number is reduced too. Although not so important, the swapoff() performance improves too because one synchronize_rcu() call during swapoff() is deleted. [ying.huang@intel.com: fix bad swap file entry warning] Link: http://lkml.kernel.org/r/20190531024102.21723-1-ying.huang@intel.com Link: http://lkml.kernel.org/r/20190527082714.12151-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hugh Dickins <hughd@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12mm, swap: fix race between swapoff and some swap operationsHuang Ying
When swapin is performed, after getting the swap entry information from the page table, system will swap in the swap entry, without any lock held to prevent the swap device from being swapoff. This may cause the race like below, CPU 1 CPU 2 ----- ----- do_swap_page swapin_readahead __read_swap_cache_async swapoff swapcache_prepare p->swap_map = NULL __swap_duplicate p->swap_map[?] /* !!! NULL pointer access */ Because swapoff is usually done when system shutdown only, the race may not hit many people in practice. But it is still a race need to be fixed. To fix the race, get_swap_device() is added to check whether the specified swap entry is valid in its swap device. If so, it will keep the swap entry valid via preventing the swap device from being swapoff, until put_swap_device() is called. Because swapoff() is very rare code path, to make the normal path runs as fast as possible, rcu_read_lock/unlock() and synchronize_rcu() instead of reference count is used to implement get/put_swap_device(). >From get_swap_device() to put_swap_device(), RCU reader side is locked, so synchronize_rcu() in swapoff() will wait until put_swap_device() is called. In addition to swap_map, cluster_info, etc. data structure in the struct swap_info_struct, the swap cache radix tree will be freed after swapoff, so this patch fixes the race between swap cache looking up and swapoff too. Races between some other swap cache usages and swapoff are fixed too via calling synchronize_rcu() between clearing PageSwapCache() and freeing swap cache data structure. Another possible method to fix this is to use preempt_off() + stop_machine() to prevent the swap device from being swapoff when its data structure is being accessed. The overhead in hot-path of both methods is similar. The advantages of RCU based method are, 1. stop_machine() may disturb the normal execution code path on other CPUs. 2. File cache uses RCU to protect its radix tree. If the similar mechanism is used for swap cache too, it is easier to share code between them. 3. RCU is used to protect swap cache in total_swapcache_pages() and exit_swap_address_space() already. The two mechanisms can be merged to simplify the logic. Link: http://lkml.kernel.org/r/20190522015423.14418-1-ying.huang@intel.com Fixes: 235b62176712 ("mm/swap: add cluster lock") Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com> Not-nacked-by: Hugh Dickins <hughd@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-05Revert "mm: page cache: store only head pages in i_pages"Linus Torvalds
This reverts commit 5fd4ca2d84b249f0858ce28cf637cf25b61a398f. Mikhail Gavrilov reports that it causes the VM_BUG_ON_PAGE() in __delete_from_swap_cache() to trigger: page:ffffd6d34dff0000 refcount:1 mapcount:1 mapping:ffff97812323a689 index:0xfecec363 anon flags: 0x17fffe00080034(uptodate|lru|active|swapbacked) raw: 0017fffe00080034 ffffd6d34c67c508 ffffd6d3504b8d48 ffff97812323a689 raw: 00000000fecec363 0000000000000000 0000000100000000 ffff978433ace000 page dumped because: VM_BUG_ON_PAGE(entry != page) page->mem_cgroup:ffff978433ace000 ------------[ cut here ]------------ kernel BUG at mm/swap_state.c:170! invalid opcode: 0000 [#1] SMP NOPTI CPU: 1 PID: 221 Comm: kswapd0 Not tainted 5.2.0-0.rc2.git0.1.fc31.x86_64 #1 Hardware name: System manufacturer System Product Name/ROG STRIX X470-I GAMING, BIOS 2202 04/11/2019 RIP: 0010:__delete_from_swap_cache+0x20d/0x240 Code: 30 65 48 33 04 25 28 00 00 00 75 4a 48 83 c4 38 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 c7 c6 2f dc 0f 8a 48 89 c7 e8 93 1b fd ff <0f> 0b 48 c7 c6 a8 74 0f 8a e8 85 1b fd ff 0f 0b 48 c7 c6 a8 7d 0f RSP: 0018:ffffa982036e7980 EFLAGS: 00010046 RAX: 0000000000000021 RBX: 0000000000000040 RCX: 0000000000000006 RDX: 0000000000000000 RSI: 0000000000000086 RDI: ffff97843d657900 RBP: 0000000000000001 R08: ffffa982036e7835 R09: 0000000000000535 R10: ffff97845e21a46c R11: ffffa982036e7835 R12: ffff978426387120 R13: 0000000000000000 R14: ffffd6d34dff0040 R15: ffffd6d34dff0000 FS: 0000000000000000(0000) GS:ffff97843d640000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00002cba88ef5000 CR3: 000000078a97c000 CR4: 00000000003406e0 Call Trace: delete_from_swap_cache+0x46/0xa0 try_to_free_swap+0xbc/0x110 swap_writepage+0x13/0x70 pageout.isra.0+0x13c/0x350 shrink_page_list+0xc14/0xdf0 shrink_inactive_list+0x1e5/0x3c0 shrink_node_memcg+0x202/0x760 shrink_node+0xe0/0x470 balance_pgdat+0x2d1/0x510 kswapd+0x220/0x420 kthread+0xfb/0x130 ret_from_fork+0x22/0x40 and it's not immediately obvious why it happens. It's too late in the rc cycle to do anything but revert for now. Link: https://lore.kernel.org/lkml/CABXGCsN9mYmBD-4GaaeW_NrDu+FDXLzr_6x+XNxfmFV6QkYCDg@mail.gmail.com/ Reported-and-bisected-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Suggested-by: Jan Kara <jack@suse.cz> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Matthew Wilcox <willy@infradead.org> Cc: Kirill Shutemov <kirill@shutemov.name> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-14mm: page cache: store only head pages in i_pagesMatthew Wilcox
Transparent Huge Pages are currently stored in i_pages as pointers to consecutive subpages. This patch changes that to storing consecutive pointers to the head page in preparation for storing huge pages more efficiently in i_pages. Large parts of this are "inspired" by Kirill's patch https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/ [willy@infradead.org: fix swapcache pages] Link: http://lkml.kernel.org/r/20190324155441.GF10344@bombadil.infradead.org [kirill@shutemov.name: hugetlb stores pages in page cache differently] Link: http://lkml.kernel.org/r/20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1 Link: http://lkml.kernel.org/r/20190307153051.18815-1-willy@infradead.org Signed-off-by: Matthew Wilcox <willy@infradead.org> Acked-by: Jan Kara <jack@suse.cz> Reviewed-by: Kirill Shutemov <kirill@shutemov.name> Reviewed-and-tested-by: Song Liu <songliubraving@fb.com> Tested-by: William Kucharski <william.kucharski@oracle.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Tested-by: Qian Cai <cai@lca.pw> Cc: Hugh Dickins <hughd@google.com> Cc: Song Liu <liu.song.a23@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-05mm: swap: add comment for swap_vma_readaheadYang Shi
swap_vma_readahead()'s comment is missing, just add it. Link: http://lkml.kernel.org/r/1546543673-108536-2-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Huang Ying <ying.huang@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Hugh Dickins <hughd@google.com Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-05mm: swap: check if swap backing device is congested or notYang Shi
Swap readahead would read in a few pages regardless if the underlying device is busy or not. It may incur long waiting time if the device is congested, and it may also exacerbate the congestion. Use inode_read_congested() to check if the underlying device is busy or not like what file page readahead does. Get inode from swap_info_struct. Although we can add inode information in swap_address_space (address_space->host), it may lead some unexpected side effect, i.e. it may break mapping_cap_account_dirty(). Using inode from swap_info_struct seems simple and good enough. Just does the check in vma_cluster_readahead() since swap_vma_readahead() is just used for non-rotational device which much less likely has congestion than traditional HDD. Although swap slots may be consecutive on swap partition, it still may be fragmented on swap file. This check would help to reduce excessive stall for such case. The test with page_fault1 of will-it-scale (sometimes tracing may just show runtest.py that is the wrapper script of page_fault1), which basically launches NR_CPU threads to generate 128MB anonymous pages for each thread, on my virtual machine with congested HDD shows long tail latency is reduced significantly. Without the patch page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); With the patch runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); [akpm@linux-foundation.org: code cleanup] [yang.shi@linux.alibaba.com: add comment] Link: http://lkml.kernel.org/r/bbc7bda7-62d0-df1a-23ef-d369e865bdca@linux.alibaba.com Link: http://lkml.kernel.org/r/1546543673-108536-1-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> Acked-by: Tim Chen <tim.c.chen@intel.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Huang Ying <ying.huang@intel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Hugh Dickins <hughd@google.com Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-28Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-daxLinus Torvalds
Pull XArray conversion from Matthew Wilcox: "The XArray provides an improved interface to the radix tree data structure, providing locking as part of the API, specifying GFP flags at allocation time, eliminating preloading, less re-walking the tree, more efficient iterations and not exposing RCU-protected pointers to its users. This patch set 1. Introduces the XArray implementation 2. Converts the pagecache to use it 3. Converts memremap to use it The page cache is the most complex and important user of the radix tree, so converting it was most important. Converting the memremap code removes the only other user of the multiorder code, which allows us to remove the radix tree code that supported it. I have 40+ followup patches to convert many other users of the radix tree over to the XArray, but I'd like to get this part in first. The other conversions haven't been in linux-next and aren't suitable for applying yet, but you can see them in the xarray-conv branch if you're interested" * 'xarray' of git://git.infradead.org/users/willy/linux-dax: (90 commits) radix tree: Remove multiorder support radix tree test: Convert multiorder tests to XArray radix tree tests: Convert item_delete_rcu to XArray radix tree tests: Convert item_kill_tree to XArray radix tree tests: Move item_insert_order radix tree test suite: Remove multiorder benchmarking radix tree test suite: Remove __item_insert memremap: Convert to XArray xarray: Add range store functionality xarray: Move multiorder_check to in-kernel tests xarray: Move multiorder_shrink to kernel tests xarray: Move multiorder account test in-kernel radix tree test suite: Convert iteration test to XArray radix tree test suite: Convert tag_tagged_items to XArray radix tree: Remove radix_tree_clear_tags radix tree: Remove radix_tree_maybe_preload_order radix tree: Remove split/join code radix tree: Remove radix_tree_update_node_t page cache: Finish XArray conversion dax: Convert page fault handlers to XArray ...
2018-10-26mm: workingset: tell cache transitions from workingset thrashingJohannes Weiner
Refaults happen during transitions between workingsets as well as in-place thrashing. Knowing the difference between the two has a range of applications, including measuring the impact of memory shortage on the system performance, as well as the ability to smarter balance pressure between the filesystem cache and the swap-backed workingset. During workingset transitions, inactive cache refaults and pushes out established active cache. When that active cache isn't stale, however, and also ends up refaulting, that's bonafide thrashing. Introduce a new page flag that tells on eviction whether the page has been active or not in its lifetime. This bit is then stored in the shadow entry, to classify refaults as transitioning or thrashing. How many page->flags does this leave us with on 32-bit? 20 bits are always page flags 21 if you have an MMU 23 with the zone bits for DMA, Normal, HighMem, Movable 29 with the sparsemem section bits 30 if PAE is enabled 31 with this patch. So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA nodes. If that's not enough, the system can switch to discontigmem and re-gain the 6 or 7 sparsemem section bits. Link: http://lkml.kernel.org/r/20180828172258.3185-3-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Daniel Drake <drake@endlessm.com> Tested-by: Suren Baghdasaryan <surenb@google.com> Cc: Christopher Lameter <cl@linux.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <jweiner@fb.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Enderborg <peter.enderborg@sony.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vinayak Menon <vinmenon@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-21page cache: Finish XArray conversionMatthew Wilcox
With no more radix tree API users left, we can drop the GFP flags and use xa_init() instead of INIT_RADIX_TREE(). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21mm: Convert delete_from_swap_cache to XArrayMatthew Wilcox
Both callers of __delete_from_swap_cache have the swp_entry_t already, so pass that in to make constructing the XA_STATE easier. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21mm: Convert add_to_swap_cache to XArrayMatthew Wilcox
Combine __add_to_swap_cache and add_to_swap_cache into one function since there is no more need to preload. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-06-12treewide: kvzalloc() -> kvcalloc()Kees Cook
The kvzalloc() function has a 2-factor argument form, kvcalloc(). This patch replaces cases of: kvzalloc(a * b, gfp) with: kvcalloc(a * b, gfp) as well as handling cases of: kvzalloc(a * b * c, gfp) with: kvzalloc(array3_size(a, b, c), gfp) as it's slightly less ugly than: kvcalloc(array_size(a, b), c, gfp) This does, however, attempt to ignore constant size factors like: kvzalloc(4 * 1024, gfp) though any constants defined via macros get caught up in the conversion. Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant. The Coccinelle script used for this was: // Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@ ( kvzalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | kvzalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) ) // Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@ ( kvzalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(char) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(u8) * COUNT + COUNT , ...) | kvzalloc( - sizeof(__u8) * COUNT + COUNT , ...) | kvzalloc( - sizeof(char) * COUNT + COUNT , ...) | kvzalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) ) // 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@ ( - kvzalloc + kvcalloc ( - sizeof(TYPE) * (COUNT_ID) + COUNT_ID, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * COUNT_ID + COUNT_ID, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * (COUNT_CONST) + COUNT_CONST, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * COUNT_CONST + COUNT_CONST, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (COUNT_ID) + COUNT_ID, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * COUNT_ID + COUNT_ID, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (COUNT_CONST) + COUNT_CONST, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * COUNT_CONST + COUNT_CONST, sizeof(THING) , ...) ) // 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@ - kvzalloc + kvcalloc ( - SIZE * COUNT + COUNT, SIZE , ...) // 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@ ( kvzalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) ) // 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@ ( kvzalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kvzalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) ) // 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@ ( kvzalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) ) // Any remaining multi-factor products, first at least 3-factor products, // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@ ( kvzalloc(C1 * C2 * C3, ...) | kvzalloc( - (E1) * E2 * E3 + array3_size(E1, E2, E3) , ...) | kvzalloc( - (E1) * (E2) * E3 + array3_size(E1, E2, E3) , ...) | kvzalloc( - (E1) * (E2) * (E3) + array3_size(E1, E2, E3) , ...) | kvzalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) ) // And then all remaining 2 factors products when they're not all constants, // keeping sizeof() as the second factor argument. @@ expression THING, E1, E2; type TYPE; constant C1, C2, C3; @@ ( kvzalloc(sizeof(THING) * C2, ...) | kvzalloc(sizeof(TYPE) * C2, ...) | kvzalloc(C1 * C2 * C3, ...) | kvzalloc(C1 * C2, ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * (E2) + E2, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * E2 + E2, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (E2) + E2, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * E2 + E2, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - (E1) * E2 + E1, E2 , ...) | - kvzalloc + kvcalloc ( - (E1) * (E2) + E1, E2 , ...) | - kvzalloc + kvcalloc ( - E1 * E2 + E1, E2 , ...) ) Signed-off-by: Kees Cook <keescook@chromium.org>
2018-06-07mm, memcontrol: move swap charge handling into get_swap_page()Tejun Heo
Patch series "mm, memcontrol: Implement memory.swap.events", v2. This patchset implements memory.swap.events which contains max and fail events so that userland can monitor and respond to swap running out. This patch (of 2): get_swap_page() is always followed by mem_cgroup_try_charge_swap(). This patch moves mem_cgroup_try_charge_swap() into get_swap_page() and makes get_swap_page() call the function even after swap allocation failure. This simplifies the callers and consolidates memcg related logic and will ease adding swap related memcg events. Link: http://lkml.kernel.org/r/20180416230934.GH1911913@devbig577.frc2.facebook.com Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Roman Gushchin <guro@fb.com> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11page cache: use xa_lockMatthew Wilcox
Remove the address_space ->tree_lock and use the xa_lock newly added to the radix_tree_root. Rename the address_space ->page_tree to ->i_pages, since we don't really care that it's a tree. [willy@infradead.org: fix nds32, fs/dax.c] Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Jeff Layton <jlayton@redhat.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05mm/swap_state.c: make bool enable_vma_readahead and swap_vma_readahead() staticColin Ian King
The bool enable_vma_readahead and swap_vma_readahead() are local to the source and do not need to be in global scope, so make them static. Cleans up sparse warnings: mm/swap_state.c:41:6: warning: symbol 'enable_vma_readahead' was not declared. Should it be static? mm/swap_state.c:742:13: warning: symbol 'swap_vma_readahead' was not declared. Should it be static? Link: http://lkml.kernel.org/r/20180223164852.5159-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05mm: swap: unify cluster-based and vma-based swap readaheadMinchan Kim
This patch makes do_swap_page() not need to be aware of two different swap readahead algorithms. Just unify cluster-based and vma-based readahead function call. Link: http://lkml.kernel.org/r/1509520520-32367-3-git-send-email-minchan@kernel.org Link: http://lkml.kernel.org/r/20180220085249.151400-3-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05mm: swap: clean up swap readaheadMinchan Kim
When I see recent change of swap readahead, I am very unhappy about current code structure which diverges two swap readahead algorithm in do_swap_page. This patch is to clean it up. Main motivation is that fault handler doesn't need to be aware of readahead algorithms but just should call swapin_readahead. As first step, this patch cleans up a little bit but not perfect (I just separate for review easier) so next patch will make the goal complete. [minchan@kernel.org: do not check readahead flag with THP anon] Link: http://lkml.kernel.org/r/874lm83zho.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20180227232611.169883-1-minchan@kernel.org Link: http://lkml.kernel.org/r/1509520520-32367-2-git-send-email-minchan@kernel.org Link: http://lkml.kernel.org/r/20180220085249.151400-2-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15mm: remove cold parameter for release_pagesMel Gorman
All callers of release_pages claim the pages being released are cache hot. As no one cares about the hotness of pages being released to the allocator, just ditch the parameter. No performance impact is expected as the overhead is marginal. The parameter is removed simply because it is a bit stupid to have a useless parameter copied everywhere. Link: http://lkml.kernel.org/r/20171018075952.10627-7-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15mm/swap_state.c: declare a few variables as __read_mostlyChangbin Du
These global variables are only set during initialization or rarely change, so declare them as __read_mostly. Link: http://lkml.kernel.org/r/1507802349-5554-1-git-send-email-changbin.du@intel.com Signed-off-by: Changbin Du <changbin.du@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15mm, swap: fix false error message in __swp_swapcount()Huang Ying
When a page fault occurs for a swap entry, the physical swap readahead (not the VMA base swap readahead) may readahead several swap entries after the fault swap entry. The readahead algorithm calculates some of the swap entries to readahead via increasing the offset of the fault swap entry without checking whether they are beyond the end of the swap device and it relys on the __swp_swapcount() and swapcache_prepare() to check it. Although __swp_swapcount() checks for the swap entry passed in, it will complain with the error message as follow for the expected invalid swap entry. This may make the end users confused. swap_info_get: Bad swap offset entry 0200f8a7 To fix the false error message, the swap entry checking is added in swapin_readahead() to avoid to pass the out-of-bound swap entries and the swap entry reserved for the swap header to __swp_swapcount() and swapcache_prepare(). Link: http://lkml.kernel.org/r/20171102054225.22897-1-ying.huang@intel.com Fixes: e8c26ab60598 ("mm/swap: skip readahead for unreferenced swap slots") Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reported-by: Christian Kujau <lists@nerdbynature.de> Acked-by: Minchan Kim <minchan@kernel.org> Suggested-by: Minchan Kim <minchan@kernel.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.11+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-10-13mm, swap: use page-cluster as max window of VMA based swap readaheadHuang Ying
When the VMA based swap readahead was introduced, a new knob /sys/kernel/mm/swap/vma_ra_max_order was added as the max window of VMA swap readahead. This is to make it possible to use different max window for VMA based readahead and original physical readahead. But Minchan Kim pointed out that this will cause a regression because setting page-cluster sysctl to zero cannot disable swap readahead with the change. To fix the regression, the page-cluster sysctl is used as the max window of both the VMA based swap readahead and original physical swap readahead. If more fine grained control is needed in the future, more knobs can be added as the subordinate knobs of the page-cluster sysctl. The vma_ra_max_order knob is deleted. Because the knob was introduced in v4.14-rc1, and this patch is targeting being merged before v4.14 releasing, there should be no existing users of this newly added ABI. Link: http://lkml.kernel.org/r/20171011070847.16003-1-ying.huang@intel.com Fixes: ec560175c0b6fce ("mm, swap: VMA based swap readahead") Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reported-by: Minchan Kim <minchan@kernel.org> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-03mm: fix data corruption caused by lazyfree pageShaohua Li
MADV_FREE clears pte dirty bit and then marks the page lazyfree (clear SwapBacked). There is no lock to prevent the page is added to swap cache between these two steps by page reclaim. If page reclaim finds such page, it will simply add the page to swap cache without pageout the page to swap because the page is marked as clean. Next time, page fault will read data from the swap slot which doesn't have the original data, so we have a data corruption. To fix issue, we mark the page dirty and pageout the page. However, we shouldn't dirty all pages which is clean and in swap cache. swapin page is swap cache and clean too. So we only dirty page which is added into swap cache in page reclaim, which shouldn't be swapin page. As Minchan suggested, simply dirty the page in add_to_swap can do the job. Fixes: 802a3a92ad7a ("mm: reclaim MADV_FREE pages") Link: http://lkml.kernel.org/r/08c84256b007bf3f63c91d94383bd9eb6fee2daa.1506446061.git.shli@fb.com Signed-off-by: Shaohua Li <shli@fb.com> Reported-by: Artem Savkov <asavkov@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hillf Danton <hdanton@sina.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: <stable@vger.kernel.org> [4.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, swap: add sysfs interface for VMA based swap readaheadHuang Ying
The sysfs interface to control the VMA based swap readahead is added as follow, /sys/kernel/mm/swap/vma_ra_enabled Enable the VMA based swap readahead algorithm, or use the original global swap readahead algorithm. /sys/kernel/mm/swap/vma_ra_max_order Set the max order of the readahead window size for the VMA based swap readahead algorithm. The corresponding ABI documentation is added too. Link: http://lkml.kernel.org/r/20170807054038.1843-5-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, swap: VMA based swap readaheadHuang Ying
The swap readahead is an important mechanism to reduce the swap in latency. Although pure sequential memory access pattern isn't very popular for anonymous memory, the space locality is still considered valid. In the original swap readahead implementation, the consecutive blocks in swap device are readahead based on the global space locality estimation. But the consecutive blocks in swap device just reflect the order of page reclaiming, don't necessarily reflect the access pattern in virtual memory. And the different tasks in the system may have different access patterns, which makes the global space locality estimation incorrect. In this patch, when page fault occurs, the virtual pages near the fault address will be readahead instead of the swap slots near the fault swap slot in swap device. This avoid to readahead the unrelated swap slots. At the same time, the swap readahead is changed to work on per-VMA from globally. So that the different access patterns of the different VMAs could be distinguished, and the different readahead policy could be applied accordingly. The original core readahead detection and scaling algorithm is reused, because it is an effect algorithm to detect the space locality. The test and result is as follow, Common test condition ===================== Test Machine: Xeon E5 v3 (2 sockets, 72 threads, 32G RAM) Swap device: NVMe disk Micro-benchmark with combined access pattern ============================================ vm-scalability, sequential swap test case, 4 processes to eat 50G virtual memory space, repeat the sequential memory writing until 300 seconds. The first round writing will trigger swap out, the following rounds will trigger sequential swap in and out. At the same time, run vm-scalability random swap test case in background, 8 processes to eat 30G virtual memory space, repeat the random memory write until 300 seconds. This will trigger random swap-in in the background. This is a combined workload with sequential and random memory accessing at the same time. The result (for sequential workload) is as follow, Base Optimized ---- --------- throughput 345413 KB/s 414029 KB/s (+19.9%) latency.average 97.14 us 61.06 us (-37.1%) latency.50th 2 us 1 us latency.60th 2 us 1 us latency.70th 98 us 2 us latency.80th 160 us 2 us latency.90th 260 us 217 us latency.95th 346 us 369 us latency.99th 1.34 ms 1.09 ms ra_hit% 52.69% 99.98% The original swap readahead algorithm is confused by the background random access workload, so readahead hit rate is lower. The VMA-base readahead algorithm works much better. Linpack ======= The test memory size is bigger than RAM to trigger swapping. Base Optimized ---- --------- elapsed_time 393.49 s 329.88 s (-16.2%) ra_hit% 86.21% 98.82% The score of base and optimized kernel hasn't visible changes. But the elapsed time reduced and readahead hit rate improved, so the optimized kernel runs better for startup and tear down stages. And the absolute value of readahead hit rate is high, shows that the space locality is still valid in some practical workloads. Link: http://lkml.kernel.org/r/20170807054038.1843-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, swap: fix swap readahead markingHuang Ying
In the original implementation, it is possible that the existing pages in the swap cache (not newly readahead) could be marked as the readahead pages. This will cause the statistics of swap readahead be wrong and influence the swap readahead algorithm too. This is fixed via marking a page as the readahead page only if it is newly allocated and read from the disk. When testing with linpack, after the fixing the swap readahead hit rate increased from ~66% to ~86%. Link: http://lkml.kernel.org/r/20170807054038.1843-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, swap: add swap readahead hit statisticsHuang Ying
Patch series "mm, swap: VMA based swap readahead", v4. The swap readahead is an important mechanism to reduce the swap in latency. Although pure sequential memory access pattern isn't very popular for anonymous memory, the space locality is still considered valid. In the original swap readahead implementation, the consecutive blocks in swap device are readahead based on the global space locality estimation. But the consecutive blocks in swap device just reflect the order of page reclaiming, don't necessarily reflect the access pattern in virtual memory space. And the different tasks in the system may have different access patterns, which makes the global space locality estimation incorrect. In this patchset, when page fault occurs, the virtual pages near the fault address will be readahead instead of the swap slots near the fault swap slot in swap device. This avoid to readahead the unrelated swap slots. At the same time, the swap readahead is changed to work on per-VMA from globally. So that the different access patterns of the different VMAs could be distinguished, and the different readahead policy could be applied accordingly. The original core readahead detection and scaling algorithm is reused, because it is an effect algorithm to detect the space locality. In addition to the swap readahead changes, some new sysfs interface is added to show the efficiency of the readahead algorithm and some other swap statistics. This new implementation will incur more small random read, on SSD, the improved correctness of estimation and readahead target should beat the potential increased overhead, this is also illustrated in the test results below. But on HDD, the overhead may beat the benefit, so the original implementation will be used by default. The test and result is as follow, Common test condition ===================== Test Machine: Xeon E5 v3 (2 sockets, 72 threads, 32G RAM) Swap device: NVMe disk Micro-benchmark with combined access pattern ============================================ vm-scalability, sequential swap test case, 4 processes to eat 50G virtual memory space, repeat the sequential memory writing until 300 seconds. The first round writing will trigger swap out, the following rounds will trigger sequential swap in and out. At the same time, run vm-scalability random swap test case in background, 8 processes to eat 30G virtual memory space, repeat the random memory write until 300 seconds. This will trigger random swap-in in the background. This is a combined workload with sequential and random memory accessing at the same time. The result (for sequential workload) is as follow, Base Optimized ---- --------- throughput 345413 KB/s 414029 KB/s (+19.9%) latency.average 97.14 us 61.06 us (-37.1%) latency.50th 2 us 1 us latency.60th 2 us 1 us latency.70th 98 us 2 us latency.80th 160 us 2 us latency.90th 260 us 217 us latency.95th 346 us 369 us latency.99th 1.34 ms 1.09 ms ra_hit% 52.69% 99.98% The original swap readahead algorithm is confused by the background random access workload, so readahead hit rate is lower. The VMA-base readahead algorithm works much better. Linpack ======= The test memory size is bigger than RAM to trigger swapping. Base Optimized ---- ----