linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@zip.com.au>
To: Joel Becker <jlbec@evilplan.org>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>,
	Jeff Garzik <jgarzik@mandrakesoft.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: fadvise syscall?
Date: Mon, 18 Mar 2002 00:14:19 -0800	[thread overview]
Message-ID: <3C95A1DB.CA13A822@zip.com.au> (raw)
In-Reply-To: <3C945635.4050101@mandrakesoft.com> <3C945A5A.9673053F@zip.com.au> <3C945D7D.8040703@mandrakesoft.com> <5.1.0.14.2.20020317131910.0522b490@pop.cus.cam.ac.uk> <20020318080531.W4836@parcelfarce.linux.theplanet.co.uk>

Joel Becker wrote:
> 
> On Sun, Mar 17, 2002 at 01:41:37PM +0000, Anton Altaparmakov wrote:
> > We don't need fadvise IMHO. That is what open(2) is for. The streaming
> > request you are asking for is just a normal open(2). It will do read ahead
> > which is perfect for streaming (of data size << RAM size in its current form).
> 
>         A quick real world example of where fadvise can work well.
> Imagine a database appliction that doesn't use O_DIRECT (for whatever
> reason, could even be that they don't trust the linux implementation yet
> :-).

O_DIRECT is broken against RAID0 (at least) in 2.5 at present.  The
RAID driver gets sent BIOs which straddle two or more chunks and RAID
spits out lots of unpleasant warnings.  Neil has been informed...

>  So, this database gets a query.  That query requires a full table
> scan, so it calls fadvise(fd, F_SEQUENTIAL).  Then another query does
> row-specific access, and caching helps.  So it wants to turn off
> F_SEQUENTIAL.

It'd probably be smarter for the application to hold two fds against
the same file for this sort of access pattern.


-

  parent reply	other threads:[~2002-03-18  8:16 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-03-17  8:39 fadvise syscall? Jeff Garzik
2002-03-17  8:56 ` Andrew Morton
2002-03-17  9:10   ` Jeff Garzik
2002-03-17 23:59     ` Anton Altaparmakov
2002-03-17 13:41   ` Anton Altaparmakov
2002-03-17 14:31     ` Simon Richter
2002-03-17 14:56       ` Jan Hudec
2002-03-17 15:00     ` Anton Altaparmakov
2002-03-17 19:20     ` Joel Becker
2002-03-18  7:28     ` Jeff Garzik
2002-03-18  7:55       ` Andrew Morton
2002-03-18  8:07         ` Jeff Garzik
2002-03-18  8:17           ` Andrew Morton
2002-03-18 16:41         ` Richard Gooch
2002-03-18 19:00           ` Andrew Morton
2002-03-18 19:15             ` Richard Gooch
2002-03-22 16:05       ` Pavel Machek
2002-03-24  6:38         ` Stevie O
2002-03-24 11:24           ` Pavel Machek
2002-03-24 12:52             ` Anton Altaparmakov
2002-03-25 11:12               ` Pavel Machek
2002-03-18  8:05     ` Joel Becker
2002-03-18  8:10       ` Jeff Garzik
2002-03-18  8:20         ` Joel Becker
2002-03-18  8:14       ` Andrew Morton [this message]
2002-03-18 14:39         ` Martin K. Petersen
2002-03-18 19:15           ` Andrew Morton
2002-03-18 19:42             ` Martin K. Petersen
2002-03-19 20:08               ` Eric W. Biederman
2002-03-19 23:38                 ` Martin K. Petersen
2002-03-17 20:18   ` Richard Gooch
2002-03-17 15:13 ` Ken Hirsch
2002-03-17 17:14 ` Anton Altaparmakov
2002-03-17 18:31   ` Mark Mielke
2002-03-17 18:35   ` Ken Hirsch
2002-03-17 19:06   ` Anton Altaparmakov
2002-03-17 20:19     ` Ken Hirsch
2002-03-18  0:12     ` Anton Altaparmakov
     [not found]       ` <a73ujs$5mc$1@cesium.transmeta.com>
2002-03-18  8:58         ` Jan Hudec
2002-03-18 10:08           ` Jeff Garzik
2002-03-18 17:29             ` Mark Mielke

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=3C95A1DB.CA13A822@zip.com.au \
    --to=akpm@zip.com.au \
    --cc=aia21@cam.ac.uk \
    --cc=jgarzik@mandrakesoft.com \
    --cc=jlbec@evilplan.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).