summaryrefslogtreecommitdiffstats
path: root/net/sched/sch_generic.c
diff options
context:
space:
mode:
Diffstat (limited to 'net/sched/sch_generic.c')
-rw-r--r--net/sched/sch_generic.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 5d81a4478514..ffad48109a22 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -25,6 +25,7 @@
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <linux/slab.h>
+#include <net/sch_generic.h>
#include <net/pkt_sched.h>
#include <net/dst.h>
@@ -896,3 +897,39 @@ void dev_shutdown(struct net_device *dev)
WARN_ON(timer_pending(&dev->watchdog_timer));
}
+
+void psched_ratecfg_precompute(struct psched_ratecfg *r, u32 rate)
+{
+ u64 factor;
+ u64 mult;
+ int shift;
+
+ r->rate_bps = rate << 3;
+ r->shift = 0;
+ r->mult = 1;
+ /*
+ * Calibrate mult, shift so that token counting is accurate
+ * for smallest packet size (64 bytes). Token (time in ns) is
+ * computed as (bytes * 8) * NSEC_PER_SEC / rate_bps. It will
+ * work as long as the smallest packet transfer time can be
+ * accurately represented in nanosec.
+ */
+ if (r->rate_bps > 0) {
+ /*
+ * Higher shift gives better accuracy. Find the largest
+ * shift such that mult fits in 32 bits.
+ */
+ for (shift = 0; shift < 16; shift++) {
+ r->shift = shift;
+ factor = 8LLU * NSEC_PER_SEC * (1 << r->shift);
+ mult = div64_u64(factor, r->rate_bps);
+ if (mult > UINT_MAX)
+ break;
+ }
+
+ r->shift = shift - 1;
+ factor = 8LLU * NSEC_PER_SEC * (1 << r->shift);
+ r->mult = div64_u64(factor, r->rate_bps);
+ }
+}
+EXPORT_SYMBOL(psched_ratecfg_precompute);