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Re: TAKE - Delay Buffer Changes

To: dcox@xxxxxxxxxx
Subject: Re: TAKE - Delay Buffer Changes
From: Rajagopal Ananthanarayanan <ananth@xxxxxxx>
Date: Wed, 28 Feb 2001 08:31:59 -0800
Cc: Linux-XFS <linux-xfs@xxxxxxxxxxx>
References: <200102270040.f1R0eAV02973@xxxxxxxxxxxxxxxxx> <3A9CF982.18BFE19@xxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
Danny wrote:
        [ ... ]
> too, and this "hang" may have been due to that.  I've NOT seen the
> "0-order allocation failed" messages, which was my main sticking point.

Memory balancing is handled much better now that XFS plays
"by the rules" of Linux using standard IO paths & daemons.
It's still possible to get allocation failures on HIGHMEM (> 900M memory)
systems on allocations of bounce buffers ... again this is
a problem in linux HIGHMEM IO, there are some discussions on
linux-kernel about reserving a pool of lowmem to allocate for bouncing.

>         Also, either because I'm using the "-o logbufs=4,logbsize=32768" mount
> option, or the recent changes, or both, the Bonnie block writes went
> from 14+ MB/sec to 20+, and the block reads went from 9+ MB/sec to 10+.

Any sequential IO changes are not likely due to log changes.
After the delay buffer change I'm seeing close to raw I/O
speeds on my scsi disk on sequential writes (reads were already
close to optimal).



Rajagopal Ananthanarayanan ("ananth")
Member Technical Staff, SGI.

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