From: Michal Hocko <mhocko@kernel.org> To: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Thomas Hellstrom <thellstrom@vmware.com>, akpm@linux-foundation.org, penguin-kernel@I-love.SAKURA.ne.jp, linux-kernel@vger.kernel.org, linux-mm@kvack.org, hpa@zytor.com, chris@chris-wilson.co.uk, hch@lst.de, mingo@elte.hu, jszhang@marvell.com, joelaf@google.com, joaodias@google.com, willy@infradead.org, tglx@linutronix.de, stable@vger.kernel.org Subject: Re: [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context Date: Wed, 5 Apr 2017 12:42:25 +0200 [thread overview] Message-ID: <20170405104224.GH6035@dhcp22.suse.cz> (raw) In-Reply-To: <d28bc808-0aab-d36a-f401-9925680fd131@virtuozzo.com> On Wed 05-04-17 13:31:23, Andrey Ryabinin wrote: > On 04/04/2017 12:41 PM, Michal Hocko wrote: > > On Thu 30-03-17 17:48:39, Andrey Ryabinin wrote: > >> From: Andrey Ryabinin <aryabinin@virtuozzo.com> > >> Subject: mm/vmalloc: allow to call vfree() in atomic context fix > >> > >> Don't spawn worker if we already purging. > >> > >> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> > > > > I would rather put this into a separate patch. Ideally with some numners > > as this is an optimization... > > > > It's quite simple optimization and don't think that this deserves to > be a separate patch. I disagree. I am pretty sure nobody will remember after few years. I do not want to push too hard on this but I can tell you from my own experience that we used to do way too many optimizations like that in the past and they tend to be real head scratchers these days. Moreover people just tend to build on top of them without understadning and then chances are quite high that they are no longer relevant anymore. > But I did some measurements though. With enabled VMAP_STACK=y and > NR_CACHED_STACK changed to 0 running fork() 100000 times gives this: > > With optimization: > > ~ # grep try_purge /proc/kallsyms > ffffffff811d0dd0 t try_purge_vmap_area_lazy > ~ # perf stat --repeat 10 -ae workqueue:workqueue_queue_work --filter 'function == 0xffffffff811d0dd0' ./fork > > Performance counter stats for 'system wide' (10 runs): > > 15 workqueue:workqueue_queue_work ( +- 0.88% ) > > 1.615368474 seconds time elapsed ( +- 0.41% ) > > > Without optimization: > ~ # grep try_purge /proc/kallsyms > ffffffff811d0dd0 t try_purge_vmap_area_lazy > ~ # perf stat --repeat 10 -ae workqueue:workqueue_queue_work --filter 'function == 0xffffffff811d0dd0' ./fork > > Performance counter stats for 'system wide' (10 runs): > > 30 workqueue:workqueue_queue_work ( +- 1.31% ) > > 1.613231060 seconds time elapsed ( +- 0.38% ) > > > So there is no measurable difference on the test itself, but we queue > twice more jobs without this optimization. It should decrease load of > kworkers. And this is really valueable for the changelog! Thanks! -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Thomas Hellstrom <thellstrom@vmware.com>, akpm@linux-foundation.org, penguin-kernel@I-love.SAKURA.ne.jp, linux-kernel@vger.kernel.org, linux-mm@kvack.org, hpa@zytor.com, chris@chris-wilson.co.uk, hch@lst.de, mingo@elte.hu, jszhang@marvell.com, joelaf@google.com, joaodias@google.com, willy@infradead.org, tglx@linutronix.de, stable@vger.kernel.org Subject: Re: [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context Date: Wed, 5 Apr 2017 12:42:25 +0200 [thread overview] Message-ID: <20170405104224.GH6035@dhcp22.suse.cz> (raw) In-Reply-To: <d28bc808-0aab-d36a-f401-9925680fd131@virtuozzo.com> On Wed 05-04-17 13:31:23, Andrey Ryabinin wrote: > On 04/04/2017 12:41 PM, Michal Hocko wrote: > > On Thu 30-03-17 17:48:39, Andrey Ryabinin wrote: > >> From: Andrey Ryabinin <aryabinin@virtuozzo.com> > >> Subject: mm/vmalloc: allow to call vfree() in atomic context fix > >> > >> Don't spawn worker if we already purging. > >> > >> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> > > > > I would rather put this into a separate patch. Ideally with some numners > > as this is an optimization... > > > > It's quite simple optimization and don't think that this deserves to > be a separate patch. I disagree. I am pretty sure nobody will remember after few years. I do not want to push too hard on this but I can tell you from my own experience that we used to do way too many optimizations like that in the past and they tend to be real head scratchers these days. Moreover people just tend to build on top of them without understadning and then chances are quite high that they are no longer relevant anymore. > But I did some measurements though. With enabled VMAP_STACK=y and > NR_CACHED_STACK changed to 0 running fork() 100000 times gives this: > > With optimization: > > ~ # grep try_purge /proc/kallsyms > ffffffff811d0dd0 t try_purge_vmap_area_lazy > ~ # perf stat --repeat 10 -ae workqueue:workqueue_queue_work --filter 'function == 0xffffffff811d0dd0' ./fork > > Performance counter stats for 'system wide' (10 runs): > > 15 workqueue:workqueue_queue_work ( +- 0.88% ) > > 1.615368474 seconds time elapsed ( +- 0.41% ) > > > Without optimization: > ~ # grep try_purge /proc/kallsyms > ffffffff811d0dd0 t try_purge_vmap_area_lazy > ~ # perf stat --repeat 10 -ae workqueue:workqueue_queue_work --filter 'function == 0xffffffff811d0dd0' ./fork > > Performance counter stats for 'system wide' (10 runs): > > 30 workqueue:workqueue_queue_work ( +- 1.31% ) > > 1.613231060 seconds time elapsed ( +- 0.38% ) > > > So there is no measurable difference on the test itself, but we queue > twice more jobs without this optimization. It should decrease load of > kworkers. And this is really valueable for the changelog! Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-04-05 10:43 UTC|newest] Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-30 10:27 [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context Andrey Ryabinin 2017-03-30 10:27 ` Andrey Ryabinin 2017-03-30 10:27 ` Andrey Ryabinin 2017-03-30 10:27 ` [PATCH 2/4] x86/ldt: use vfree() instead of vfree_atomic() Andrey Ryabinin 2017-03-30 10:27 ` Andrey Ryabinin 2017-03-31 8:05 ` Thomas Gleixner 2017-03-31 8:05 ` Thomas Gleixner 2017-03-30 10:27 ` [PATCH 3/4] kernel/fork: use vfree() instead of vfree_atomic() to free thread stack Andrey Ryabinin 2017-03-30 10:27 ` Andrey Ryabinin 2017-03-30 10:27 ` [PATCH 4/4] mm/vmalloc: remove vfree_atomic() Andrey Ryabinin 2017-03-30 10:27 ` Andrey Ryabinin 2017-03-30 17:18 ` Matthew Wilcox 2017-03-30 17:18 ` Matthew Wilcox 2017-03-30 15:27 ` Andrey Ryabinin 2017-03-30 15:27 ` Andrey Ryabinin 2017-04-04 9:40 ` Michal Hocko 2017-04-04 9:40 ` Michal Hocko 2017-03-30 12:00 ` [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context Thomas Hellstrom 2017-03-30 12:00 ` Thomas Hellstrom 2017-03-30 12:00 ` Thomas Hellstrom 2017-03-30 14:48 ` Andrey Ryabinin 2017-03-30 14:48 ` Andrey Ryabinin 2017-03-30 14:48 ` Andrey Ryabinin 2017-03-30 15:04 ` Thomas Hellstrom 2017-03-30 15:04 ` Thomas Hellstrom 2017-03-30 15:04 ` Thomas Hellstrom 2017-04-04 9:41 ` Michal Hocko 2017-04-04 9:41 ` Michal Hocko 2017-04-04 9:49 ` Thomas Hellstrom 2017-04-04 9:49 ` Thomas Hellstrom 2017-04-04 9:49 ` Thomas Hellstrom 2017-04-05 10:31 ` Andrey Ryabinin 2017-04-05 10:31 ` Andrey Ryabinin 2017-04-05 10:31 ` Andrey Ryabinin 2017-04-05 10:42 ` Michal Hocko [this message] 2017-04-05 10:42 ` Michal Hocko 2017-04-05 11:42 ` Vlastimil Babka 2017-04-05 11:42 ` Vlastimil Babka 2017-04-05 12:14 ` Michal Hocko 2017-04-05 12:14 ` Michal Hocko 2017-03-30 22:22 ` Andrew Morton 2017-03-30 22:22 ` Andrew Morton 2017-03-30 22:22 ` Andrew Morton 2017-03-31 7:12 ` Joel Fernandes 2017-03-31 7:12 ` Joel Fernandes 2017-03-31 9:26 ` Andrey Ryabinin 2017-03-31 9:26 ` Andrey Ryabinin 2017-03-31 9:26 ` Andrey Ryabinin 2017-04-04 9:36 ` Michal Hocko 2017-04-04 9:36 ` Michal Hocko 2017-04-04 9:38 ` Michal Hocko 2017-04-04 9:38 ` Michal Hocko 2017-04-12 12:49 ` [PATCH v2 0/5] " Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` [PATCH v2 1/5] mm/vmalloc: " Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` [PATCH v2 2/5] x86/ldt: use vfree() instead of vfree_atomic() Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` [PATCH v2 3/5] kernel/fork: use vfree() instead of vfree_atomic() to free thread stack Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` [PATCH v2 4/5] mm/vmalloc: remove vfree_atomic() Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin 2017-04-12 12:49 ` [PATCH v2 5/5] mm/vmalloc: Don't spawn workers if somebody already purging Andrey Ryabinin 2017-04-12 12:49 ` Andrey Ryabinin
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20170405104224.GH6035@dhcp22.suse.cz \ --to=mhocko@kernel.org \ --cc=akpm@linux-foundation.org \ --cc=aryabinin@virtuozzo.com \ --cc=chris@chris-wilson.co.uk \ --cc=hch@lst.de \ --cc=hpa@zytor.com \ --cc=joaodias@google.com \ --cc=joelaf@google.com \ --cc=jszhang@marvell.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=mingo@elte.hu \ --cc=penguin-kernel@I-love.SAKURA.ne.jp \ --cc=stable@vger.kernel.org \ --cc=tglx@linutronix.de \ --cc=thellstrom@vmware.com \ --cc=willy@infradead.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.