From: JoonSoo Kim <js1304@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
Rik van Riel <riel@redhat.com>, Minchan Kim <minchan@kernel.org>,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>
Subject: Re: [PATCH 2/3] mm, slub: count freed pages via rcu as this task's reclaimed_slab
Date: Wed, 10 Apr 2013 23:24:38 +0900 [thread overview]
Message-ID: <CAAmzW4PZ4ODR5gjYczmoNBYP-yk7q6MTNdOO4A_qux0xCFH_Gg@mail.gmail.com> (raw)
In-Reply-To: <0000013df43c9afa-0cba04ce-4a5b-435e-acc4-5ee5a1cfeb6b-000000@email.amazonses.com>
2013/4/10 Christoph Lameter <cl@linux.com>:
> On Wed, 10 Apr 2013, Joonsoo Kim wrote:
>
>> Hello, Christoph.
>>
>> On Tue, Apr 09, 2013 at 02:28:06PM +0000, Christoph Lameter wrote:
>> > On Tue, 9 Apr 2013, Joonsoo Kim wrote:
>> >
>> > > Currently, freed pages via rcu is not counted for reclaimed_slab, because
>> > > it is freed in rcu context, not current task context. But, this free is
>> > > initiated by this task, so counting this into this task's reclaimed_slab
>> > > is meaningful to decide whether we continue reclaim, or not.
>> > > So change code to count these pages for this task's reclaimed_slab.
>> >
>> > slab->reclaim_state guides the reclaim actions in vmscan.c. With this
>> > patch slab->reclaim_state could get quite a high value without new pages being
>> > available for allocation. slab->reclaim_state will only be updated
>> > when the RCU period ends.
>>
>> Okay.
>>
>> In addition, there is a little place who use SLAB_DESTROY_BY_RCU.
>> I will drop this patch[2/3] and [3/3] for next spin.
>
> What you have discoverd is an issue that we have so far overlooked. Could
> you add comments to both places explaining the situation?
Yes, I can.
> RCU is used for
> some inode and the dentry cache. Failing to account for these frees could
> pose a problem. One solution would be to ensure that we get through an RCU
> quiescent period in the slabs reclaim. If we can ensure that then your
> patch may be ok.
Hmm... I don't perfectly understand RCU code and it's quiescent
period. But, yes, it
can be one of possible solutions in my quick thought. Currently, I
have no ability to
do that, so I skip to think about this.
Thanks.
>
> --
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next prev parent reply other threads:[~2013-04-10 14:24 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-09 1:21 [PATCH 1/3] mm, vmscan: count accidental reclaimed pages failed to put into lru Joonsoo Kim
2013-04-09 1:21 ` [PATCH 2/3] mm, slub: count freed pages via rcu as this task's reclaimed_slab Joonsoo Kim
2013-04-09 9:38 ` Simon Jeons
2013-04-09 14:32 ` Christoph Lameter
2013-04-10 3:20 ` Simon Jeons
2013-04-10 13:54 ` Christoph Lameter
2013-04-11 3:46 ` Simon Jeons
2013-04-11 15:03 ` Christoph Lameter
2013-04-09 14:28 ` Christoph Lameter
2013-04-10 5:26 ` Joonsoo Kim
2013-04-10 13:57 ` Christoph Lameter
2013-04-10 14:24 ` JoonSoo Kim [this message]
2013-04-09 1:21 ` [PATCH 3/3] mm, slab: " Joonsoo Kim
2013-04-09 5:55 ` [PATCH 1/3] mm, vmscan: count accidental reclaimed pages failed to put into lru Minchan Kim
2013-04-10 5:48 ` Joonsoo Kim
2013-04-10 6:03 ` Minchan Kim
2013-04-09 7:19 ` Wanpeng Li
2013-04-09 7:19 ` Wanpeng Li
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