From: Johannes Weiner <hannes@cmpxchg.org>
To: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 5/6] mm: workingset: size shadow nodes lru basing on file cache size
Date: Tue, 9 Feb 2016 18:14:12 -0500 [thread overview]
Message-ID: <20160209231412.GA32427@cmpxchg.org> (raw)
In-Reply-To: <26fb2cef8be75a27eae79e91b0f8351b468ab9d0.1455025246.git.vdavydov@virtuozzo.com>
On Tue, Feb 09, 2016 at 04:55:53PM +0300, Vladimir Davydov wrote:
> A page is activated on refault if the refault distance stored in the
> corresponding shadow entry is less than the number of active file pages.
> Since active file pages can't occupy more than half memory, we assume
> that the maximal effective refault distance can't be greater than half
> the number of present pages and size the shadow nodes lru list
> appropriately. Generally speaking, this assumption is correct, but it
> can result in wasting a considerable chunk of memory on stale shadow
> nodes in case the portion of file pages is small, e.g. if a workload
> mostly uses anonymous memory.
>
> To sort this out, we need to compute the size of shadow nodes lru basing
> not on the maximal possible, but the current size of file cache. We
> could take the size of active file lru for the maximal refault distance,
> but active lru is pretty unstable - it can shrink dramatically at
> runtime possibly disrupting workingset detection logic.
>
> Instead we assume that the maximal refault distance equals half the
> total number of file cache pages. This will protect us against active
> file lru size fluctuations while still being correct, because size of
> active lru is normally maintained lower than size of inactive lru.
>
> Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Begrudgingly, because I don't think it matters that much and I like
the dumber version. But it's a reasonable change nonetheless.
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next prev parent reply other threads:[~2016-02-09 23:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-09 13:55 [PATCH v2 0/6] mm: workingset: make shadow node shrinker memcg aware Vladimir Davydov
2016-02-09 13:55 ` [PATCH v2 1/6] mm: memcontrol: enable kmem accounting for all cgroups in the legacy hierarchy Vladimir Davydov
2016-02-09 13:55 ` [PATCH v2 2/6] mm: vmscan: pass root_mem_cgroup instead of NULL to memcg aware shrinker Vladimir Davydov
2016-02-09 13:55 ` [PATCH v2 3/6] mm: memcontrol: zap memcg_kmem_online helper Vladimir Davydov
2016-02-09 13:55 ` [PATCH v2 4/6] radix-tree: account radix_tree_node to memory cgroup Vladimir Davydov
2016-02-09 13:55 ` [PATCH v2 5/6] mm: workingset: size shadow nodes lru basing on file cache size Vladimir Davydov
2016-02-09 23:14 ` Johannes Weiner [this message]
2016-02-09 13:55 ` [PATCH v2 6/6] mm: workingset: make shadow node shrinker memcg aware Vladimir Davydov
2016-02-09 23:15 ` Johannes Weiner
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