On 10/18/2017 03:42 AM, Kemi Wang wrote: > This is the second step which introduces a tunable interface that allow > numa stats configurable for optimizing zone_statistics(), as suggested by > Dave Hansen and Ying Huang. > > ========================================================================= > When page allocation performance becomes a bottleneck and you can tolerate > some possible tool breakage and decreased numa counter precision, you can > do: > echo 0 > /proc/sys/vm/numa_stat > In this case, numa counter update is ignored. We can see about > *4.8%*(185->176) drop of cpu cycles per single page allocation and reclaim > on Jesper's page_bench01 (single thread) and *8.1%*(343->315) drop of cpu > cycles per single page allocation and reclaim on Jesper's page_bench03 (88 > threads) running on a 2-Socket Broadwell-based server (88 threads, 126G > memory). > > Benchmark link provided by Jesper D Brouer(increase loop times to > 10000000): > https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/ > bench > > ========================================================================= > When page allocation performance is not a bottleneck and you want all > tooling to work, you can do: > echo 1 > /proc/sys/vm/numa_stat > This is system default setting. > > Many thanks to Michal Hocko, Dave Hansen, Ying Huang and Vlastimil Babka > for comments to help improve the original patch. > > ChangeLog: > V4->V5 > a) Scope vm_numa_stat_lock into the sysctl handler function, as suggested > by Michal Hocko; > b) Only allow 0/1 value when setting a value to numa_stat at userspace, > that would keep the possibility for add auto mode in future (e.g. 2 for > auto mode), as suggested by Michal Hocko. > > V3->V4 > a) Get rid of auto mode of numa stats, and may add it back if necessary, > as alignment before; > b) Skip NUMA_INTERLEAVE_HIT counter update when numa stats is disabled, > as reported by Andrey Ryabinin. See commit "de55c8b2519" for details > c) Remove extern declaration for those clear_numa_ function, and make > them static in vmstat.c, as suggested by Vlastimil Babka. > > V2->V3: > a) Propose a better way to use jump label to eliminate the overhead of > branch selection in zone_statistics(), as inspired by Ying Huang; > b) Add a paragraph in commit log to describe the way for branch target > selection; > c) Use a more descriptive name numa_stats_mode instead of vmstat_mode, > and change the description accordingly, as suggested by Michal Hocko; > d) Make this functionality NUMA-specific via ifdef > > V1->V2: > a) Merge to one patch; > b) Use jump label to eliminate the overhead of branch selection; > c) Add a single-time log message at boot time to help tell users what > happened. > > Reported-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> > Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxx> > Suggested-by: Ying Huang <ying.huang@xxxxxxxxx> > Signed-off-by: Kemi Wang <kemi.wang@xxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
