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From: Andrew Morton <akpm@zip.com.au>
To: "Martin K. Petersen" <mkp@mkp.net>
Cc: Joel Becker <jlbec@evilplan.org>,
	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 11:15:33 -0800	[thread overview]
Message-ID: <3C963CD5.8E371FF@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> <3C95A1DB.CA13A822@zip.com.au> <yq1bsdmq6so.fsf@austin.mkp.net>

"Martin K. Petersen" wrote:
> 
> >>>>> "Andrew" == Andrew Morton <akpm@zip.com.au> writes:
> 
> Andrew> O_DIRECT is broken against RAID0 (at least) in 2.5 at present.
> Andrew> The RAID driver gets sent BIOs which straddle two or more
> Andrew> chunks and RAID spits out lots of unpleasant warnings.  Neil
> Andrew> has been informed...
> 
> Yep.  I've been porting my original kiobuf based request splitter to
> biobufs.  It's almost there, I've just been extremely busy with
> something else for a while.
> 
> It's not only when you straddle chunks.  The current code does not
> handle requests straddling RAID zones either.

google fails me - where does your kiobuf-based splitter live?

I'm curious to know how this will all work.  Will it take a
large BIO and split it into a number of smaller, newly allocated
BIOs?  That would be kinda sad, IMO - the current bio-per-bh
allocations in the normal I/O path are really expensive, and
it seems wrong to take a large BIO, split it into lots of
teeny ones and then reassemble all the way down at the driver
level.

If that's really the only way in which we can solve this problem,
would it not be better to pass information up to the higher layer,
telling it when the BIO which is currently under assembly cannot
be grown further?  Say, blk_can_i_add_more_stuff_to_this_bio()?

Anyway.  I'm interested.  O_DIRECT is a bit of a weird curiosity,
but I'm working on making these big-BIO code paths *the* way in which
data gets to and from disk.  It needs to be efficient ;)

-

  reply	other threads:[~2002-03-18 19:17 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
2002-03-18 14:39         ` Martin K. Petersen
2002-03-18 19:15           ` Andrew Morton [this message]
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

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