From: Jens Axboe <axboe@kernel.dk>
To: David N <android.wm.edu@gmail.com>
Cc: fio@vger.kernel.org
Subject: Re: Random vs Sequential Read in FIO
Date: Thu, 21 Feb 2013 09:38:43 +0100 [thread overview]
Message-ID: <20130221083843.GD25617@kernel.dk> (raw)
In-Reply-To: <CACTzACVBXK7nKXHCaaOxSE=2YN+WKjaDPtQqZkfgL1jNyVhxLg@mail.gmail.com>
On Thu, Feb 21 2013, David N wrote:
> Hi,
>
> I was using FIO to get response time of random reads and sequential
> reads from phone's flash memory and I got like 9x greater response
> time for random read. Since there is no seek time as in conventional
> rotating storage, I'm wondering where this huge jump of random IO
> response time comes from? How is the total IO delay actually
> calculated in FIO?
One option is that your sequential reads are coalesced and issued as one
command, whereas random flash reads will still trigger a tread and
tstream pause for each one. You need to look at device stats with the
workload to see what the ratio between fio-request:device-request is.
--
Jens Axboe
prev parent reply other threads:[~2013-02-21 8:40 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-21 5:35 Random vs Sequential Read in FIO David N
2013-02-21 8:38 ` Jens Axboe [this message]
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