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b=Qk1BzDEkUh8eX2jCubVXULNJFRlE1UzB+PV7iS3fwj6mM6QzArrwqLvNel/srJIY5HgxpJ izfpEc/x1uI1EbdYPuBPPSbzjc5sziYV48bbtVJ8R59j4d1JqiPaDdDVjKJXGP0w2cYvvt 6tFJ5UTAELAmC+jWsVvnGAplRYzZIvg= X-Stat-Signature: 94uu1hfx1a4q86poeqh1yc83m7hok7mm X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A82CC1A001D Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=TMDmeULT; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf19.hostedemail.com: domain of ryncsn@gmail.com designates 209.85.216.50 as permitted sender) smtp.mailfrom=ryncsn@gmail.com X-Rspam-User: X-HE-Tag: 1661849451-866111 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Michal Hocko =E4=BA=8E2022=E5=B9=B48=E6=9C=8830=E6=97=A5= =E5=91=A8=E4=BA=8C 15:01=E5=86=99=E9=81=93=EF=BC=9A > > On Tue 30-08-22 13:59:49, Kairui Song wrote: > > From: Kairui Song > > > > cgroup_memory_noswap is used in many hot path, so make it a static key > > to lower the kernel overhead. > > > > Using 8G of ZRAM as SWAP, benchmark using `perf stat -d -d -d --repeat = 100` > > with the following code snip in a non-root cgroup: > > > > #include > > #include > > #include > > #include > > #define MB 1024UL * 1024UL > > int main(int argc, char **argv){ > > void *p =3D mmap(NULL, 8000 * MB, PROT_READ | PROT_WRITE, > > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > > memset(p, 0xff, 8000 * MB); > > madvise(p, 8000 * MB, MADV_PAGEOUT); > > memset(p, 0xff, 8000 * MB); > > return 0; > > } > > > > Before: > > 7,021.43 msec task-clock # 0.967 CPUs utili= zed ( +- 0.03% ) > > 4,010 context-switches # 573.853 /sec = ( +- 0.01% ) > > 0 cpu-migrations # 0.000 /sec > > 2,052,057 page-faults # 293.661 K/sec = ( +- 0.00% ) > > 12,616,546,027 cycles # 1.805 GHz = ( +- 0.06% ) (39.92%) > > 156,823,666 stalled-cycles-frontend # 1.25% frontend c= ycles idle ( +- 0.10% ) (40.25%) > > 310,130,812 stalled-cycles-backend # 2.47% backend cy= cles idle ( +- 4.39% ) (40.73%) > > 18,692,516,591 instructions # 1.49 insn per c= ycle > > # 0.01 stalled cy= cles per insn ( +- 0.04% ) (40.75%) > > 4,907,447,976 branches # 702.283 M/sec = ( +- 0.05% ) (40.30%) > > 13,002,578 branch-misses # 0.26% of all bra= nches ( +- 0.08% ) (40.48%) > > 7,069,786,296 L1-dcache-loads # 1.012 G/sec = ( +- 0.03% ) (40.32%) > > 649,385,847 L1-dcache-load-misses # 9.13% of all L1-= dcache accesses ( +- 0.07% ) (40.10%) > > 1,485,448,688 L1-icache-loads # 212.576 M/sec = ( +- 0.15% ) (39.49%) > > 31,628,457 L1-icache-load-misses # 2.13% of all L1-= icache accesses ( +- 0.40% ) (39.57%) > > 6,667,311 dTLB-loads # 954.129 K/sec = ( +- 0.21% ) (39.50%) > > 5,668,555 dTLB-load-misses # 86.40% of all dTL= B cache accesses ( +- 0.12% ) (39.03%) > > 765 iTLB-loads # 109.476 /sec = ( +- 21.81% ) (39.44%) > > 4,370,351 iTLB-load-misses # 214320.09% of all i= TLB cache accesses ( +- 1.44% ) (39.86%) > > 149,207,254 L1-dcache-prefetches # 21.352 M/sec = ( +- 0.13% ) (40.27%) > > > > 7.25869 +- 0.00203 seconds time elapsed ( +- 0.03% ) > > > > After: > > 6,576.16 msec task-clock # 0.953 CPUs utili= zed ( +- 0.10% ) > > 4,020 context-switches # 605.595 /sec = ( +- 0.01% ) > > 0 cpu-migrations # 0.000 /sec > > 2,052,056 page-faults # 309.133 K/sec = ( +- 0.00% ) > > 11,967,619,180 cycles # 1.803 GHz = ( +- 0.36% ) (38.76%) > > 161,259,240 stalled-cycles-frontend # 1.38% frontend c= ycles idle ( +- 0.27% ) (36.58%) > > 253,605,302 stalled-cycles-backend # 2.16% backend cy= cles idle ( +- 4.45% ) (34.78%) > > 19,328,171,892 instructions # 1.65 insn per c= ycle > > # 0.01 stalled cy= cles per insn ( +- 0.10% ) (31.46%) > > 5,213,967,902 branches # 785.461 M/sec = ( +- 0.18% ) (30.68%) > > 12,385,170 branch-misses # 0.24% of all bra= nches ( +- 0.26% ) (34.13%) > > 7,271,687,822 L1-dcache-loads # 1.095 G/sec = ( +- 0.12% ) (35.29%) > > 649,873,045 L1-dcache-load-misses # 8.93% of all L1-= dcache accesses ( +- 0.11% ) (41.41%) > > 1,950,037,608 L1-icache-loads # 293.764 M/sec = ( +- 0.33% ) (43.11%) > > 31,365,566 L1-icache-load-misses # 1.62% of all L1-= icache accesses ( +- 0.39% ) (45.89%) > > 6,767,809 dTLB-loads # 1.020 M/sec = ( +- 0.47% ) (48.42%) > > 6,339,590 dTLB-load-misses # 95.43% of all dTL= B cache accesses ( +- 0.50% ) (46.60%) > > 736 iTLB-loads # 110.875 /sec = ( +- 1.79% ) (48.60%) > > 4,314,836 iTLB-load-misses # 518653.73% of all i= TLB cache accesses ( +- 0.63% ) (42.91%) > > 144,950,156 L1-dcache-prefetches # 21.836 M/sec = ( +- 0.37% ) (41.39%) > > > > 6.89935 +- 0.00703 seconds time elapsed ( +- 0.10% ) > > Do you happen to have a perf profile before and after to see which of > the paths really benefits from this? No I don't have a clear profile data about which path benefit the most. The performance benchmark result can be stably reproduced, but perf record & report & diff doesn't seems too helpful, as I can't see a significant change of any single symbols. There are quite a few callers of memcg_swap_enabled and do_memsw_account (which also calls memcg_swap_enabled), to me, it seems multiple pieces of optimization caused an overall improvement. And a lower overhead for the branch predictor may also help in general. Any other suggestion about how to collect such data?