From: Jeff Moyer <jmoyer@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Shaohua Li <shli@kernel.org>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH]block: make auto block plug flush threshold per-disk based
Date: Mon, 09 Apr 2012 10:13:12 -0400 [thread overview]
Message-ID: <x498vi5803r.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <4F7F2A3D.3010700@kernel.dk> (Jens Axboe's message of "Fri, 06 Apr 2012 11:39:09 -0600")
Jens Axboe <axboe@kernel.dk> writes:
> On 2012-04-06 11:27, Shaohua Li wrote:
>> We do auto block plug flush to reduce latency, the threshold is 16
>> requests. This works well if the task is accessing one or two drives.
>> The problem is if the task is accessing a raid 0 device and the raid
>> disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have
>> heavy lock contention.
>>
>> This patch makes the threshold per-disk based. The latency should be
>> still ok accessing one or two drives. The setup with application
>> accessing a lot of drives in the meantime uaually is big machine,
>> avoiding lock contention is more important, because any contention
>> will actually increase latency.
>
> Thanks, applied. It should have been per-queue all along, so this
> makes a lot of sense.
Yeah, I had noticed this before when looking over the code. Makes
sense.
Acked-by: Jeff Moyer <jmoyer@redhat.com>
prev parent reply other threads:[~2012-04-09 14:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-06 17:27 Shaohua Li
2012-04-06 17:39 ` Jens Axboe
2012-04-09 14:13 ` Jeff Moyer [this message]
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