From: Vladimir Davydov <vdavydov@virtuozzo.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>, <linux-mm@kvack.org>,
<cgroups@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<kernel-team@fb.com>
Subject: Re: [PATCH 1/3] mm: migrate: do not touch page->mem_cgroup of live pages
Date: Wed, 3 Feb 2016 12:20:09 +0300 [thread overview]
Message-ID: <20160203092009.GE21016@esperanza> (raw)
In-Reply-To: <1454109573-29235-2-git-send-email-hannes@cmpxchg.org>
On Fri, Jan 29, 2016 at 06:19:31PM -0500, Johannes Weiner wrote:
> Changing a page's memcg association complicates dealing with the page,
> so we want to limit this as much as possible. Page migration e.g. does
> not have to do that. Just like page cache replacement, it can forcibly
> charge a replacement page, and then uncharge the old page when it gets
> freed. Temporarily overcharging the cgroup by a single page is not an
> issue in practice, and charging is so cheap nowadays that this is much
> preferrable to the headache of messing with live pages.
>
> The only place that still changes the page->mem_cgroup binding of live
> pages is when pages move along with a task to another cgroup. But that
> path isolates the page from the LRU, takes the page lock, and the move
> lock (lock_page_memcg()). That means page->mem_cgroup is always stable
> in callers that have the page isolated from the LRU or locked. Lighter
> unlocked paths, like writeback accounting, can use lock_page_memcg().
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
WARNING: multiple messages have this Message-ID (diff)
From: Vladimir Davydov <vdavydov@virtuozzo.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 1/3] mm: migrate: do not touch page->mem_cgroup of live pages
Date: Wed, 3 Feb 2016 12:20:09 +0300 [thread overview]
Message-ID: <20160203092009.GE21016@esperanza> (raw)
In-Reply-To: <1454109573-29235-2-git-send-email-hannes@cmpxchg.org>
On Fri, Jan 29, 2016 at 06:19:31PM -0500, Johannes Weiner wrote:
> Changing a page's memcg association complicates dealing with the page,
> so we want to limit this as much as possible. Page migration e.g. does
> not have to do that. Just like page cache replacement, it can forcibly
> charge a replacement page, and then uncharge the old page when it gets
> freed. Temporarily overcharging the cgroup by a single page is not an
> issue in practice, and charging is so cheap nowadays that this is much
> preferrable to the headache of messing with live pages.
>
> The only place that still changes the page->mem_cgroup binding of live
> pages is when pages move along with a task to another cgroup. But that
> path isolates the page from the LRU, takes the page lock, and the move
> lock (lock_page_memcg()). That means page->mem_cgroup is always stable
> in callers that have the page isolated from the LRU or locked. Lighter
> unlocked paths, like writeback accounting, can use lock_page_memcg().
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Cc: Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-team-b10kYP2dOMg@public.gmane.org
Subject: Re: [PATCH 1/3] mm: migrate: do not touch page->mem_cgroup of live pages
Date: Wed, 3 Feb 2016 12:20:09 +0300 [thread overview]
Message-ID: <20160203092009.GE21016@esperanza> (raw)
In-Reply-To: <1454109573-29235-2-git-send-email-hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
On Fri, Jan 29, 2016 at 06:19:31PM -0500, Johannes Weiner wrote:
> Changing a page's memcg association complicates dealing with the page,
> so we want to limit this as much as possible. Page migration e.g. does
> not have to do that. Just like page cache replacement, it can forcibly
> charge a replacement page, and then uncharge the old page when it gets
> freed. Temporarily overcharging the cgroup by a single page is not an
> issue in practice, and charging is so cheap nowadays that this is much
> preferrable to the headache of messing with live pages.
>
> The only place that still changes the page->mem_cgroup binding of live
> pages is when pages move along with a task to another cgroup. But that
> path isolates the page from the LRU, takes the page lock, and the move
> lock (lock_page_memcg()). That means page->mem_cgroup is always stable
> in callers that have the page isolated from the LRU or locked. Lighter
> unlocked paths, like writeback accounting, can use lock_page_memcg().
>
> Signed-off-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Acked-by: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
next prev parent reply other threads:[~2016-02-03 9:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 23:19 [PATCH 0/3] mm: memcontrol: simplify page->mem_cgroup pinning Johannes Weiner
2016-01-29 23:19 ` Johannes Weiner
2016-01-29 23:19 ` Johannes Weiner
2016-01-29 23:19 ` [PATCH 1/3] mm: migrate: do not touch page->mem_cgroup of live pages Johannes Weiner
2016-01-29 23:19 ` Johannes Weiner
2016-02-03 9:20 ` Vladimir Davydov [this message]
2016-02-03 9:20 ` Vladimir Davydov
2016-02-03 9:20 ` Vladimir Davydov
2016-02-03 13:17 ` Mateusz Guzik
2016-02-03 13:17 ` Mateusz Guzik
2016-02-03 13:17 ` Mateusz Guzik
2016-02-03 14:08 ` Vladimir Davydov
2016-02-03 14:08 ` Vladimir Davydov
2016-02-03 14:08 ` Vladimir Davydov
2016-02-03 18:35 ` Johannes Weiner
2016-02-03 18:35 ` Johannes Weiner
2016-02-04 1:39 ` Hugh Dickins
2016-02-04 1:39 ` Hugh Dickins
2016-02-04 1:39 ` Hugh Dickins
2016-02-04 19:53 ` Johannes Weiner
2016-02-04 19:53 ` Johannes Weiner
2016-02-28 23:57 ` Hugh Dickins
2016-02-28 23:57 ` Hugh Dickins
2016-01-29 23:19 ` [PATCH 2/3] mm: simplify lock_page_memcg() Johannes Weiner
2016-01-29 23:19 ` Johannes Weiner
2016-02-03 9:25 ` Vladimir Davydov
2016-02-03 9:25 ` Vladimir Davydov
2016-01-29 23:19 ` [PATCH 3/3] mm: remove unnecessary uses of lock_page_memcg() Johannes Weiner
2016-01-29 23:19 ` Johannes Weiner
2016-02-03 9:29 ` Vladimir Davydov
2016-02-03 9:29 ` Vladimir Davydov
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