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Re: [Fwd: Re: mysterious dbench results]

To: Jens Axboe <axboe@xxxxxxx>
Subject: Re: [Fwd: Re: mysterious dbench results]
From: Chaitanya Tumuluri <chait@xxxxxxxxxxxxxxxxxxxx>
Date: Tue, 20 Feb 2001 16:26:09 -0500 (EST)
Cc: Thomas Graichen <graichen@xxxxxxxxxxxxx>, Rajagopal Ananthanarayanan <ananth@xxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <3A9308B8.34D66FB3@sgi.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
> On Tue, Feb 20 2001, Rajagopal Ananthanarayanan wrote:
> > One reason for these problems could be that
> > XFS pages are not balanced properly in memory.
> > I've been experimenting with attaching buffers
> > to all XFS pages & then let the flush_dirty_buffers
> > methods take care of the write-outs. Attached is
> > an experimental patch that might improve the situation.
> > Please note that this code is work-in-progress so use
> > it only on a test system.
> 
> Another reason could be that because xfs ships kio writes,
> the elevator is effectively a noop. You don't do the merge
> check of course, but then the insertion scan is also skipped.
> So xfs ends up being a fifo request queueing.

True. So, how about trying out the following patch which is a
first cut at inserting the kiobuf requests in  LBA-ordered 
fashion in the elevator?

At the very least, it reduces the seek times which might've been
affecting kiobuf I/O performance adversely.

Cheers,
-Chait.

Attachment: kiobuf_elev.patch
Description: Text document

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