From: Shaohua Li <shli@kernel.org>
To: Roberto Spadim <roberto@spadim.com.br>
Cc: linux-raid@vger.kernel.org, neilb@suse.de, axboe@kernel.dk
Subject: Re: [patch 2/3 v3] raid1: read balance chooses idlest disk for SSD
Date: Mon, 2 Jul 2012 11:02:45 +0800 [thread overview]
Message-ID: <20120702030245.GB29770@kernel.org> (raw)
In-Reply-To: <CABYL=TpD7D0ec40fz6uo4LCPAKuxtkx5rD3JXfWTtuEYp3NLYQ@mail.gmail.com>
On Sun, Jul 01, 2012 at 11:13:42PM -0300, Roberto Spadim wrote:
> nice =) very very nice =)
> maybe to get better than this... select the disk with min(pending time)
>
> time could be estimated with something like:
> (distance * time/distance unit) + (blocks to read/write * time to
> read/write 1 block) + (non sequencial penalty time)
I didn't think there is way to measure request time. Disks support NCQ, they
can dispatch several requests at one time and finish them almost at the same
time. I used to measure this time (to make CFQ ioscheduler self tune), but
failed.
Thanks,
Shaohua
next prev parent reply other threads:[~2012-07-02 3:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-02 1:08 [patch 0/3 v3] Optimize raid1 read balance for SSD Shaohua Li
2012-07-02 1:08 ` [patch 1/3 v3] raid1: make sequential read detection per disk based Shaohua Li
2012-07-04 5:38 ` NeilBrown
2012-07-02 1:08 ` [patch 2/3 v3] raid1: read balance chooses idlest disk for SSD Shaohua Li
2012-07-02 2:13 ` Roberto Spadim
2012-07-02 3:02 ` Shaohua Li [this message]
2012-07-02 3:57 ` Roberto Spadim
2012-07-02 4:33 ` Roberto Spadim
2012-07-02 4:31 ` Roberto Spadim
2012-07-02 4:36 ` Roberto Spadim
2012-07-04 5:45 ` NeilBrown
2012-07-02 1:08 ` [patch 3/3 v3] raid1: prevent merging too large request Shaohua Li
2012-07-04 5:59 ` NeilBrown
2012-07-04 8:01 ` Shaohua Li
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