From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Michal Hocko <mhocko@kernel.org>,
akpm@linux-foundation.org, gregkh@linuxfoundation.org,
rafael@kernel.org, viro@zeniv.linux.org.uk,
darrick.wong@oracle.com, paulmck@linux.vnet.ibm.com,
josh@joshtriplett.org, rostedt@goodmis.org,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
hughd@google.com, shuah@kernel.org, robh@kernel.org,
ulf.hansson@linaro.org, aspriel@gmail.com,
vivek.gautam@codeaurora.org, robin.murphy@arm.com,
joe@perches.com, heikki.krogerus@linux.intel.com,
sfr@canb.auug.org.au, vdavydov.dev@gmail.com,
chris@chris-wilson.co.uk, aryabinin@virtuozzo.com,
willy@infradead.org, ying.huang@intel.com, shakeelb@google.com,
jbacik@fb.com, mingo@kernel.org, mhiramat@kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH RFC v2 02/10] mm: Make shrink_slab() lockless
Date: Thu, 9 Aug 2018 13:58:16 +0300 [thread overview]
Message-ID: <2e1cdec3-5133-67ec-e929-8bc174574b3a@virtuozzo.com> (raw)
In-Reply-To: <7b746367-e4bc-0e64-4e27-14fd7f06ba8f@i-love.sakura.ne.jp>
On 09.08.2018 13:37, Tetsuo Handa wrote:
> On 2018/08/09 18:21, Kirill Tkhai wrote:
>> 2)SRCU. Pros are there are no the above problems; we will have completely unlocked and
>> scalable shrink_slab(). We will also have a possibility to avoid unregistering delays,
>> like I did for superblock shrinker. There will be full scalability.
>> Cons is enabling SRCU.
>>
>
> How unregistering delays can be avoided? Since you traverse all shrinkers
> using one shrinker_srcu, synchronize_srcu(&shrinker_srcu) will block
> unregistering threads until longest inflight srcu_read_lock() user calls
> srcu_read_unlock().
Yes, but we can do synchronize_srcu() from async work like I did for the further patches.
The only thing we need is to teach shrinker::count_objects() and shrinker::scan_objects()
be safe to be called on unregistering shrinker user. The next patches do this for superblock
shrinker.
> Unless you use per shrinker counter like below, I wonder whether
> unregistering delays can be avoided...
>
> https://marc.info/?l=linux-mm&m=151060909613004
> https://marc.info/?l=linux-mm&m=151060909713005
I'm afraid these atomic_{inc,dec}(&shrinker->nr_active) may regulary drop CPU caches
on another CPUs on some workloads. Also, synchronize_rcu() is also a heavy delay.
next prev parent reply other threads:[~2018-08-09 10:58 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 15:37 [PATCH RFC 00/10] Introduce lockless shrink_slab() Kirill Tkhai
2018-08-07 15:37 ` [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled Kirill Tkhai
2018-08-08 0:55 ` Steven Rostedt
2018-08-08 1:05 ` Stephen Rothwell
2018-08-08 9:46 ` Kirill Tkhai
2018-08-08 1:08 ` Stephen Rothwell
2018-08-08 9:59 ` Kirill Tkhai
2018-08-08 11:04 ` Stephen Rothwell
2018-08-08 7:20 ` Michal Hocko
2018-08-08 10:17 ` Kirill Tkhai
2018-08-08 10:27 ` Michal Hocko
2018-08-08 21:31 ` Dave Chinner
2018-08-09 0:07 ` Matthew Wilcox
2018-08-09 7:45 ` Greg KH
2018-08-09 10:22 ` Kirill Tkhai
2018-08-08 16:13 ` Josh Triplett
2018-08-08 16:23 ` Kirill Tkhai
2018-08-08 16:30 ` Kirill Tkhai
2018-08-08 18:01 ` Josh Triplett
2018-08-08 23:02 ` Shakeel Butt
2018-08-08 23:09 ` Josh Triplett
2018-08-07 15:37 ` [PATCH RFC 02/10] mm: Make shrink_slab() lockless Kirill Tkhai
2018-08-08 11:51 ` Kirill Tkhai
2018-08-08 13:20 ` [PATCH RFC v2 " Kirill Tkhai
2018-08-09 7:14 ` Michal Hocko
2018-08-09 9:21 ` Kirill Tkhai
2018-08-09 10:37 ` Tetsuo Handa
2018-08-09 10:58 ` Kirill Tkhai [this message]
2018-08-09 11:23 ` Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 03/10] mm: Convert shrinker_rwsem to mutex Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 04/10] mm: Split unregister_shrinker() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 05/10] fs: Move list_lru_destroy() to destroy_super_work() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 06/10] fs: Shrink only (SB_ACTIVE|SB_BORN) superblocks in super_cache_scan() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 07/10] fs: Introduce struct super_operations::destroy_super() callback Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 08/10] xfs: Introduce xfs_fs_destroy_super() Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 09/10] shmem: Implement shmem_destroy_super() Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 10/10] fs: Use unregister_shrinker_delayed_{initiate, finalize} for super_block shrinker Kirill Tkhai
2018-08-08 1:12 ` [PATCH RFC 00/10] Introduce lockless shrink_slab() Stephen Rothwell
2018-08-08 5:39 ` Shakeel Butt
2018-08-08 10:18 ` Kirill Tkhai
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