Re: [PATCH 1/1] mm: prevent a race between process_mrelease and exit_mmap
From: Michal Hocko <mhocko@suse.com>
Date: 2021-11-02 07:58:24
Also in:
linux-mm, lkml
On Mon 01-11-21 08:44:58, Suren Baghdasaryan wrote: [...]
I'm with you on this one, that's why I wanted to measure the price we would pay. Below are the test results: Test: https://lore.kernel.org/all/20170725142626.GJ26723@dhcp22.suse.cz/ (local) Compiled: gcc -O2 -static test.c -o test Test machine: 128 core / 256 thread 2x AMD EPYC 7B12 64-Core Processor (family 17h) baseline (Linus master, f31531e55495ca3746fb895ffdf73586be8259fa) p50 (median) 87412 p95 168210 p99 190058 average 97843.8 stdev 29.85% unconditional mmap_write_lock in exit_mmap (last column is the change from the baseline) p50 (median) 88312 +1.03% p95 170797 +1.54% p99 191813 +0.92% average 97659.5 -0.19% stdev 32.41% unconditional mmap_write_lock in exit_mmap + Matthew's patch (last column is the change from the baseline) p50 (median) 88807 +1.60% p95 167783 -0.25% p99 187853 -1.16% average 97491.4 -0.36% stdev 30.61% stdev is quite high in all cases, so the test is very noisy. The impact seems quite low IMHO. WDYT?
Results being very noisy is what I recall as well. Thanks! -- Michal Hocko SUSE Labs