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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130221083843.GD25617@kernel.dk \
--to=axboe@kernel.dk \
--cc=android.wm.edu@gmail.com \
--cc=fio@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.