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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Matthew Wilcox <willy@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	stummala@codeaurora.org, gregkh@linuxfoundation.org,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Roman Gushchin <guro@fb.com>,
	mka@chromium.org,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	longman@redhat.com, Minchan Kim <minchan@kernel.org>,
	Huang Ying <ying.huang@intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	jbacik@fb.com, Guenter Roeck <linux@roeck-us.net>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>,
	lirongqing@baidu.com, Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker
Date: Tue, 3 Jul 2018 21:39:02 +0100	[thread overview]
Message-ID: <20180703203901.GV30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180703174744.GB4834@bombadil.infradead.org>

On Tue, Jul 03, 2018 at 10:47:44AM -0700, Matthew Wilcox wrote:
> On Tue, Jul 03, 2018 at 08:46:28AM -0700, Shakeel Butt wrote:
> > On Tue, Jul 3, 2018 at 8:27 AM Matthew Wilcox <willy@infradead.org> wrote:
> > > This will actually reduce the size of each shrinker and be more
> > > cache-efficient when calling the shrinkers.  I think we can also get
> > > rid of the shrinker_rwsem eventually, but let's leave it for now.
> > 
> > Can you explain how you envision shrinker_rwsem can be removed? I am
> > very much interested in doing that.
> 
> Sure.  Right now we have 3 uses of shrinker_rwsem -- two for adding and
> removing shrinkers to the list and one for walking the list.  If we switch
> to an IDR then we can use a spinlock for adding/removing shrinkers and
> the RCU read lock for looking up an entry in the IDR each iteration of
> the loop.
> 
> We'd need to stop the shrinker from disappearing underneath us while we
> drop the RCU lock, so we'd need a refcount in the shrinker, and to free
> the shrinkers using RCU.  We do similar things for other data structures,
> so this is all pretty well understood.

<censored>
struct super_block {
...
        struct shrinker s_shrink;       /* per-sb shrinker handle */
...
}
<censored>

What was that about refcount in the shrinker and taking over the lifetime
rules of the objects it might be embedded into, again?

  reply	other threads:[~2018-07-03 20:40 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-03 15:08 [PATCH v8 00/17] Improve shrink_slab() scalability (old complexity was O(n^2), new is O(n)) Kirill Tkhai
2018-07-03 15:08 ` [PATCH v8 01/17] list_lru: Combine code under the same define Kirill Tkhai
2018-07-03 15:08 ` [PATCH v8 02/17] mm: Introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker Kirill Tkhai
2018-07-03 15:27   ` Matthew Wilcox
2018-07-03 15:46     ` Shakeel Butt
2018-07-03 16:17       ` Kirill Tkhai
2018-07-03 17:00         ` Shakeel Butt
2018-07-03 17:32           ` Kirill Tkhai
2018-07-12 11:13             ` Kirill Tkhai
2018-07-12 11:19               ` Kirill Tkhai
2018-07-03 17:47       ` Matthew Wilcox
2018-07-03 20:39         ` Al Viro [this message]
2018-07-03 15:46     ` Kirill Tkhai
2018-07-03 17:58       ` Matthew Wilcox
2018-07-03 19:12         ` Kirill Tkhai
2018-07-03 19:19           ` Shakeel Butt
2018-07-03 19:25             ` Matthew Wilcox
2018-07-03 19:54               ` Shakeel Butt
2018-07-03 15:09 ` [PATCH v8 04/17] memcg: Move up for_each_mem_cgroup{, _tree} defines Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 05/17] mm: Assign memcg-aware shrinkers bitmap to memcg Kirill Tkhai
2018-07-03 20:50   ` Andrew Morton
2018-07-04 15:51     ` Kirill Tkhai
2018-07-05 22:10       ` Andrew Morton
2018-07-06 17:50         ` Vladimir Davydov
2018-07-05 22:50     ` Matthew Wilcox
2018-07-06 17:30     ` Vladimir Davydov
2018-07-03 15:09 ` [PATCH v8 06/17] mm: Refactoring in workingset_init() Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 07/17] fs: Refactoring in alloc_super() Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 08/17] fs: Propagate shrinker::id to list_lru Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 09/17] list_lru: Add memcg argument to list_lru_from_kmem() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 10/17] list_lru: Pass dst_memcg argument to memcg_drain_list_lru_node() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 11/17] list_lru: Pass lru " Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 12/17] mm: Export mem_cgroup_is_root() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 13/17] mm: Set bit in memcg shrinker bitmap on first list_lru item apearance Kirill Tkhai
2018-07-03 20:54   ` Andrew Morton
2018-07-03 15:11 ` [PATCH v8 14/17] mm: Iterate only over charged shrinkers during memcg shrink_slab() Kirill Tkhai
2018-07-03 20:58   ` Andrew Morton
2018-07-04 14:56     ` Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 15/17] mm: Generalize shrink_slab() calls in shrink_node() Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 16/17] mm: Add SHRINK_EMPTY shrinker methods return value Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 17/17] mm: Clear shrinker bit if there are no objects related to memcg Kirill Tkhai

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