Date: Wed, 24 Feb 2021 12:50:21 -0600 From: ebiederm@...ssion.com (Eric W. Biederman) To: Alexey Gladkov <gladkov.alexey@...il.com> Cc: kernel test robot <oliver.sang@...el.com>, 0day robot <lkp@...el.com>, LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org, ying.huang@...el.com, feng.tang@...el.com, zhengjun.xing@...el.com, io-uring@...r.kernel.org, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linux Containers <containers@...ts.linux-foundation.org>, linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <christian.brauner@...ntu.com>, Jann Horn <jannh@...gle.com>, Jens Axboe <axboe@...nel.dk>, Kees Cook <keescook@...omium.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Oleg Nesterov <oleg@...hat.com> Subject: Re: d28296d248: stress-ng.sigsegv.ops_per_sec -82.7% regression Alexey Gladkov <gladkov.alexey@...il.com> writes: > On Wed, Feb 24, 2021 at 10:54:17AM -0600, Eric W. Biederman wrote: >> kernel test robot <oliver.sang@...el.com> writes: >> >> > Greeting, >> > >> > FYI, we noticed a -82.7% regression of stress-ng.sigsegv.ops_per_sec due to commit: >> > >> > >> > commit: d28296d2484fa11e94dff65e93eb25802a443d47 ("[PATCH v7 5/7] Reimplement RLIMIT_SIGPENDING on top of ucounts") >> > url: https://github.com/0day-ci/linux/commits/Alexey-Gladkov/Count-rlimits-in-each-user-namespace/20210222-175836 >> > base: https://git.kernel.org/cgit/linux/kernel/git/shuah/linux-kselftest.git next >> > >> > in testcase: stress-ng >> > on test machine: 48 threads Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz with 112G memory >> > with following parameters: >> > >> > nr_threads: 100% >> > disk: 1HDD >> > testtime: 60s >> > class: interrupt >> > test: sigsegv >> > cpufreq_governor: performance >> > ucode: 0x42e >> > >> > >> > In addition to that, the commit also has significant impact on the >> > following tests: >> >> Thank you. Now we have a sense of where we need to test the performance >> of these changes carefully. > > One of the reasons for this is that I rolled back the patch that changed > the ucounts.count type to atomic_t. Now get_ucounts() is forced to use a > spin_lock to increase the reference count. Which given the hickups with getting a working version seems justified. Now we can add incremental patches on top to improve the performance. Eric
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