From: Muchun Song <songmuchun@bytedance.com> To: Roman Gushchin <guro@fb.com> Cc: Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@kernel.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Shakeel Butt <shakeelb@google.com>, Stephen Rothwell <sfr@canb.auug.org.au>, Chris Down <chris@chrisdown.name>, Yafang Shao <laoar.shao@gmail.com>, richard.weiyang@gmail.com, LKML <linux-kernel@vger.kernel.org>, Cgroups <cgroups@vger.kernel.org>, Linux Memory Management List <linux-mm@kvack.org> Subject: Re: [External] Re: [PATCH v2] mm: memcontrol: optimize per-lruvec stats counter memory usage Date: Wed, 9 Dec 2020 10:31:55 +0800 [thread overview] Message-ID: <CAMZfGtUMP6mz3DE7DHS55fyto=LZuQpcitt59WuwhZw8m2LqBg@mail.gmail.com> (raw) In-Reply-To: <20201209022118.GB2385286@carbon.DHCP.thefacebook.com> On Wed, Dec 9, 2020 at 10:21 AM Roman Gushchin <guro@fb.com> wrote: > > On Tue, Dec 08, 2020 at 05:51:32PM +0800, Muchun Song wrote: > > The vmstat threshold is 32 (MEMCG_CHARGE_BATCH), so the type of s32 > > of lruvec_stat_cpu is enough. And introduce struct per_cpu_lruvec_stat > > to optimize memory usage. > > > > The size of struct lruvec_stat is 304 bytes on 64 bits system. As it > > is a per-cpu structure. So with this patch, we can save 304 / 2 * ncpu > > bytes per-memcg per-node where ncpu is the number of the possible CPU. > > If there are c memory cgroup (include dying cgroup) and n NUMA node in > > the system. Finally, we can save (152 * ncpu * c * n) bytes. > > Honestly, I'm not convinced. > Say, ncpu = 32, n = 2, c = 500. We're saving <5Mb of memory. > If the machine has 128Gb of RAM, it's .000000003%. Hi Roman, When the cpu hotplug is enabled, the ncpu can be 256 on some configurations. Also, the c can be more large when there are many dying cgroup in the system. So the savings depends on the environment and configurations. Right? > > Using longs (s64) allows not to think too much about overflows > and can also be slightly faster on 64-bit machines. > > Thanks! -- Yours, Muchun
WARNING: multiple messages have this Message-ID (diff)
From: Muchun Song <songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org> To: Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org> Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Stephen Rothwell <sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>, Chris Down <chris-6Bi1550iOqEnzZ6mRAm98g@public.gmane.org>, Yafang Shao <laoar.shao-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Linux Memory Management List <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org> Subject: Re: [External] Re: [PATCH v2] mm: memcontrol: optimize per-lruvec stats counter memory usage Date: Wed, 9 Dec 2020 10:31:55 +0800 [thread overview] Message-ID: <CAMZfGtUMP6mz3DE7DHS55fyto=LZuQpcitt59WuwhZw8m2LqBg@mail.gmail.com> (raw) In-Reply-To: <20201209022118.GB2385286-lLJQVQxiE4uLfgCeKHXN1g2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org> On Wed, Dec 9, 2020 at 10:21 AM Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org> wrote: > > On Tue, Dec 08, 2020 at 05:51:32PM +0800, Muchun Song wrote: > > The vmstat threshold is 32 (MEMCG_CHARGE_BATCH), so the type of s32 > > of lruvec_stat_cpu is enough. And introduce struct per_cpu_lruvec_stat > > to optimize memory usage. > > > > The size of struct lruvec_stat is 304 bytes on 64 bits system. As it > > is a per-cpu structure. So with this patch, we can save 304 / 2 * ncpu > > bytes per-memcg per-node where ncpu is the number of the possible CPU. > > If there are c memory cgroup (include dying cgroup) and n NUMA node in > > the system. Finally, we can save (152 * ncpu * c * n) bytes. > > Honestly, I'm not convinced. > Say, ncpu = 32, n = 2, c = 500. We're saving <5Mb of memory. > If the machine has 128Gb of RAM, it's .000000003%. Hi Roman, When the cpu hotplug is enabled, the ncpu can be 256 on some configurations. Also, the c can be more large when there are many dying cgroup in the system. So the savings depends on the environment and configurations. Right? > > Using longs (s64) allows not to think too much about overflows > and can also be slightly faster on 64-bit machines. > > Thanks!
next prev parent reply other threads:[~2020-12-09 2:33 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-08 9:51 [PATCH v2] mm: memcontrol: optimize per-lruvec stats counter memory usage Muchun Song 2020-12-08 9:51 ` Muchun Song 2020-12-08 18:20 ` Shakeel Butt 2020-12-08 18:20 ` Shakeel Butt 2020-12-08 18:20 ` Shakeel Butt 2020-12-09 2:21 ` Roman Gushchin 2020-12-09 2:21 ` Roman Gushchin 2020-12-09 2:28 ` Roman Gushchin 2020-12-09 2:28 ` Roman Gushchin 2020-12-09 2:31 ` Muchun Song [this message] 2020-12-09 2:31 ` [External] " Muchun Song 2020-12-09 2:31 ` Muchun Song 2020-12-09 3:52 ` Roman Gushchin 2020-12-09 3:52 ` Roman Gushchin 2020-12-09 7:05 ` Muchun Song 2020-12-09 7:05 ` Muchun Song 2020-12-09 7:05 ` Muchun Song
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