On Mon, Jan 18, 2021 at 11:20 PM Feng Tang <feng.tang@xxxxxxxxx> wrote: > > When checking a memory cgroup related performance regression [1], > from the perf c2c profiling data, we found high false sharing for > accessing 'usage' and 'parent'. > > On 64 bit system, the 'usage' and 'parent' are close to each other, > and easy to be in one cacheline (for cacheline size == 64+ B). 'usage' > is usally written, while 'parent' is usually read as the cgroup's > hierarchical counting nature. > > So move the 'parent' to the end of the structure to make sure they > are in different cache lines. > > Following are some performance data with the patch, against > v5.11-rc1. [ In the data, A means a platform with 2 sockets 48C/96T, > B is a platform of 4 sockests 72C/144T, and if a %stddev will be > shown bigger than 2%, P100/P50 means number of test tasks equals > to 100%/50% of nr_cpu] > > will-it-scale/malloc1 > --------------------- > v5.11-rc1 v5.11-rc1+patch > > A-P100 15782 ± 2% -0.1% 15765 ± 3% will-it-scale.per_process_ops > A-P50 21511 +8.9% 23432 will-it-scale.per_process_ops > B-P100 9155 +2.2% 9357 will-it-scale.per_process_ops > B-P50 10967 +7.1% 11751 ± 2% will-it-scale.per_process_ops > > will-it-scale/pagefault2 > ------------------------ > v5.11-rc1 v5.11-rc1+patch > > A-P100 79028 +3.0% 81411 will-it-scale.per_process_ops > A-P50 183960 ± 2% +4.4% 192078 ± 2% will-it-scale.per_process_ops > B-P100 85966 +9.9% 94467 ± 3% will-it-scale.per_process_ops > B-P50 198195 +9.8% 217526 will-it-scale.per_process_ops > > fio (4k/1M is block size) > ------------------------- > v5.11-rc1 v5.11-rc1+patch > > A-P50-r-4k 16881 ± 2% +1.2% 17081 ± 2% fio.read_bw_MBps > A-P50-w-4k 3931 +4.5% 4111 ± 2% fio.write_bw_MBps > A-P50-r-1M 15178 -0.2% 15154 fio.read_bw_MBps > A-P50-w-1M 3924 +0.1% 3929 fio.write_bw_MBps > > [1].https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > Reviewed-by: Roman Gushchin <guro@xxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
