From: Jens Axboe <axboe@suse.de>
To: Andrew Morton <akpm@zip.com.au>
Cc: Andries.Brouwer@cwi.nl, linux-kernel@vger.kernel.org
Subject: Re: readahead
Date: Tue, 16 Apr 2002 21:33:04 +0200 [thread overview]
Message-ID: <20020416193304.GV1097@suse.de> (raw)
In-Reply-To: <UTC200204161910.g3GJAx009370.aeb@smtp.cwi.nl> <3CBC7A41.384FD032@zip.com.au>
On Tue, Apr 16 2002, Andrew Morton wrote:
> Andries.Brouwer@cwi.nl wrote:
> >
> > ...
> > Do these cards not have a request queue?
> >
> > The kernel views them as SCSI disks.
> > So yes, I can do
> >
> > blockdev --setra 0 /dev/sdc
> >
> > Unfortunately that does not help in the least.
> > Indeed, the only user of the readahead info is
> > readahead.c: get_max_readahead() and it does
> >
> > blk_ra_kbytes = blk_get_readahead(inode->i_dev) / 2;
> > if (blk_ra_kbytes < VM_MIN_READAHEAD)
> > blk_ra_kbytes = VM_MAX_READAHEAD;
> >
> > We need to distinguish between undefined, and explicily zero.
>
> Yup. The below (untested) patch should fix it up. Assuming
> that all drivers use blk_init_queue(), and heaven knows if
> that's the case. If not, the readahead window will have to be
set it in blk_queue_make_request(), please.
--
Jens Axboe
next prev parent reply other threads:[~2002-04-16 19:34 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-04-16 19:10 readahead Andries.Brouwer
2002-04-16 19:23 ` readahead Andrew Morton
2002-04-16 19:33 ` Jens Axboe [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-09-27 2:38 Readahead Alan Stern
2005-09-27 3:06 ` Readahead Randy.Dunlap
2005-09-27 4:24 ` Readahead Andrew Morton
2005-09-28 18:40 ` Readahead Alan Stern
2003-11-01 17:22 READAHEAD Voluspa
2003-10-30 19:23 READAHEAD age
2003-10-30 21:44 ` READAHEAD Andrew Morton
2003-10-31 7:43 ` READAHEAD Nuno Silva
2003-10-31 8:03 ` READAHEAD Andrew Morton
2003-10-31 12:20 ` READAHEAD age
2003-10-31 9:28 ` READAHEAD Andrew Morton
2003-10-31 9:29 ` READAHEAD Andrew Morton
2003-11-01 9:15 ` READAHEAD age
2003-11-03 0:15 ` READAHEAD Derek Foreman
2002-04-16 20:21 readahead Andries.Brouwer
2002-04-16 13:54 readahead Andries.Brouwer
2002-04-16 16:08 ` readahead Steven Cole
2002-04-16 18:25 ` readahead Andrew Morton
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