From: Wu Fengguang <fengguang.wu@intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jan Kara <jack@suse.cz>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/5] writeback: fix dirtied pages accounting on sub-page writes
Date: Tue, 22 Nov 2011 21:07:50 +0800 [thread overview]
Message-ID: <20111122130750.GA19929@localhost> (raw)
In-Reply-To: <1321966662.5148.35.camel@twins>
On Tue, Nov 22, 2011 at 08:57:42PM +0800, Peter Zijlstra wrote:
> On Tue, 2011-11-22 at 13:21 +0100, Jan Kara wrote:
> > > + __get_cpu_var(bdp_ratelimits)++;
> > I think you need preempt_disable() and preempt_enable() pair around
> > __get_cpu_var(). Otherwise a process could get rescheduled in the middle of
> > read-modify-write cycle...
>
> there's of course the this_cpu_inc(bdp_ratelimits); thing.
>
> On x86 that'll turn into a single insn, on others it will add the
> required preempt_disable/enable bits.
It's good to know that. But what if we don't really care which CPU
data it's increasing, and can accept losing some increases due to the
resulted race condition?
Thanks,
Fengguang
next prev parent reply other threads:[~2011-11-22 13:07 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-21 13:03 [PATCH 0/5] dirty throttling bits for 3.3 Wu Fengguang
2011-11-21 13:03 ` [PATCH 1/5] writeback: balanced_rate cannot exceed write bandwidth Wu Fengguang
2011-11-21 22:50 ` Jan Kara
2011-11-22 6:41 ` Wu Fengguang
2011-11-22 21:04 ` Jan Kara
2011-11-23 13:17 ` Wu Fengguang
2011-11-21 13:03 ` [PATCH 2/5] writeback: charge leaked page dirties to active tasks Wu Fengguang
2011-11-21 21:49 ` Andrew Morton
2011-11-21 23:46 ` Jan Kara
2011-11-22 13:35 ` Wu Fengguang
2011-11-21 13:03 ` [PATCH 3/5] writeback: fix dirtied pages accounting on sub-page writes Wu Fengguang
2011-11-22 0:11 ` Jan Kara
2011-11-22 9:21 ` Wu Fengguang
2011-11-22 12:21 ` Jan Kara
2011-11-22 12:30 ` Wu Fengguang
2011-11-22 12:48 ` Jan Kara
2011-11-22 13:02 ` Wu Fengguang
2011-11-22 12:57 ` Peter Zijlstra
2011-11-22 13:07 ` Wu Fengguang [this message]
2011-11-22 13:41 ` Wu Fengguang
2011-11-22 13:53 ` Peter Zijlstra
2011-11-22 14:11 ` Wu Fengguang
2011-11-28 13:51 ` Wu Fengguang
2011-11-21 13:03 ` [PATCH 4/5] writeback: fix dirtied pages accounting on redirty Wu Fengguang
2011-11-21 21:51 ` Andrew Morton
2011-11-22 13:59 ` Wu Fengguang
2011-11-21 13:03 ` [PATCH 5/5] writeback: dirty ratelimit - think time compensation Wu Fengguang
2011-11-23 12:44 ` [PATCH 0/5] dirty throttling bits for 3.3 Peter Zijlstra
2011-11-28 13:56 ` Wu Fengguang
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