From: Andrew Morton <akpm@zip.com.au>
To: Jens Axboe <axboe@suse.de>
Cc: William Lee Irwin III <wli@holomorphy.com>,
Giuliano Pochini <pochini@shiny.it>,
linux-kernel@vger.kernel.org, "chen,
xiangping" <chen_xiangping@emc.com>
Subject: Re: Poor read performance when sequential write presents
Date: Mon, 27 May 2002 01:22:41 -0700 [thread overview]
Message-ID: <3CF1ECD1.A1BB2CF1@zip.com.au> (raw)
In-Reply-To: <3CED4843.2783B568@zip.com.au> <XFMail.20020524105942.pochini@shiny.it> <3CEE0758.27110CAD@zip.com.au> <20020524094606.GH14918@holomorphy.com> <3CEE1035.1E67E1B8@zip.com.au> <20020527080632.GC17674@suse.de>
Jens Axboe wrote:
>
> ...
> > But in 2.5, head-activeness went away and as far as I know, IDE and SCSI are
> > treated the same. Odd.
>
> It didn't really go away, it just gets handled automatically now.
> elv_next_request() marks the request as started, in which case the i/o
> scheduler won't consider it for merging etc. SCSI removes the request
> directly after it has been marked started, while IDE leaves it on the
> queue until it completes. For IDE TCQ, the behaviour is the same as with
> SCSI.
It won't consider the active request at the head of the queue for
merging (making the request larger). But it _could_ consider the
request when making decisions about insertion (adding a new request
at the head of the queue because it's close-on-disk to the active
one). Does it do that?
-
next prev parent reply other threads:[~2002-05-27 8:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-23 14:20 Poor read performance when sequential write presents chen, xiangping
2002-05-23 19:51 ` Andrew Morton
2002-05-24 8:59 ` Giuliano Pochini
2002-05-24 9:26 ` Andrew Morton
2002-05-24 9:46 ` William Lee Irwin III
2002-05-24 10:04 ` Andrew Morton
2002-05-27 8:06 ` Jens Axboe
2002-05-27 8:22 ` Andrew Morton [this message]
2002-05-27 8:54 ` Jens Axboe
2002-05-27 9:35 ` Andrew Morton
2002-05-28 9:25 ` Jens Axboe
2002-05-28 9:36 ` Jens Axboe
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=3CF1ECD1.A1BB2CF1@zip.com.au \
--to=akpm@zip.com.au \
--cc=axboe@suse.de \
--cc=chen_xiangping@emc.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pochini@shiny.it \
--cc=wli@holomorphy.com \
/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.