From: Tejun Heo <tj@kernel.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Jens Axboe <axboe@kernel.dk>,
Mike Snitzer <snitzer@redhat.com>,
Milan Broz <gmazyland@gmail.com>,
dm-devel@redhat.com, Andi Kleen <andi@firstfloor.org>,
dm-crypt@saout.de, linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Christian Schmidt <schmidt@digadd.de>,
"Alasdair G. Kergon" <agk@redhat.com>
Subject: Re: [PATCH v2] make dm and dm-crypt forward cgroup context (was: dm-crypt parallelization patches)
Date: Thu, 11 Apr 2013 12:52:03 -0700 [thread overview]
Message-ID: <20130411195203.GA11956@mtj.dyndns.org> (raw)
In-Reply-To: <Pine.LNX.4.64.1304111544050.32536@file.rdu.redhat.com>
On Thu, Apr 11, 2013 at 03:49:20PM -0400, Mikulas Patocka wrote:
> If the bi_css pointer points to a structure that is shared between
> processes, using atomic instruction causes cache line boucing - it doesn't
> cost a few instructions, it costs 2-3 hundreds cycles.
>
> I modified the patch to use new flag BIO_DROP_CGROUP_REFCOUNT to note that
> the refcount must be decremented - if the flag is set, refcounts must be
> decremented when bio is destroyed, if it is not set, references are
> borrowed from upper layer bio.
>
> It is less bug-prone than the previous patch.
If this becomes an actual bottleneck, the right thing to do is making
css ref per-cpu. Please stop messing around with refcounting.
NACK.
--
tejun
next prev parent reply other threads:[~2013-04-11 19:52 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-26 3:47 dm-crypt performance Mikulas Patocka
2013-03-26 6:52 ` Christoph Hellwig
2013-03-26 12:27 ` [dm-devel] " Alasdair G Kergon
2013-03-26 20:05 ` Milan Broz
2013-03-26 20:28 ` Mike Snitzer
2013-03-26 20:58 ` Milan Broz
2013-03-28 18:53 ` Tejun Heo
2013-03-28 19:33 ` Vivek Goyal
2013-03-28 19:44 ` Tejun Heo
2013-03-28 20:38 ` Vivek Goyal
2013-03-28 20:45 ` Tejun Heo
2013-04-09 17:51 ` dm-crypt parallelization patches Mikulas Patocka
2013-04-09 17:57 ` Tejun Heo
2013-04-09 18:08 ` Mikulas Patocka
2013-04-09 18:10 ` Tejun Heo
2013-04-09 18:42 ` Vivek Goyal
2013-04-09 18:57 ` Tejun Heo
2013-04-09 19:13 ` Vivek Goyal
2013-04-09 19:42 ` Mikulas Patocka
2013-04-09 19:52 ` Tejun Heo
2013-04-09 20:32 ` Mikulas Patocka
2013-04-09 21:02 ` Tejun Heo
2013-04-09 21:03 ` Tejun Heo
2013-04-09 21:07 ` Vivek Goyal
2013-04-09 21:18 ` Mikulas Patocka
2013-04-10 19:24 ` Vivek Goyal
2013-04-10 23:42 ` [PATCH] make dm and dm-crypt forward cgroup context (was: dm-crypt parallelization patches) Mikulas Patocka
2013-04-10 23:50 ` Tejun Heo
2013-04-11 19:49 ` [PATCH v2] " Mikulas Patocka
2013-04-11 19:52 ` Tejun Heo [this message]
2013-04-11 20:00 ` Tejun Heo
2013-04-12 0:06 ` Mikulas Patocka
2013-04-12 0:22 ` Tejun Heo
2013-04-12 5:59 ` [PATCH v2] make dm and dm-crypt forward cgroup context Milan Broz
2013-04-12 18:17 ` [PATCH v2] make dm and dm-crypt forward cgroup context (was: dm-crypt parallelization patches) Mikulas Patocka
2013-04-12 18:01 ` Mikulas Patocka
2013-04-12 18:29 ` Tejun Heo
2013-04-15 13:02 ` Mikulas Patocka
2013-04-16 17:24 ` Tejun Heo
2013-04-16 19:41 ` Mikulas Patocka
2013-04-18 16:47 ` Mike Snitzer
2013-04-18 17:03 ` Tejun Heo
2013-05-22 18:50 ` Mike Snitzer
2013-05-22 19:48 ` Tejun Heo
2013-04-09 18:36 ` dm-crypt parallelization patches Vivek Goyal
[not found] ` <5151FF82.6090405-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2013-04-09 18:08 ` [dm-devel] dm-crypt performance Mikulas Patocka
2013-04-09 18:59 ` [dm-crypt] " Milan Broz
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