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Re: pagebuf_prepare_write doesn't kmap the page

To: Marcelo Tosatti <marcelo@xxxxxxxxxxxxxxxx>
Subject: Re: pagebuf_prepare_write doesn't kmap the page
From: Steve Lord <lord@xxxxxxx>
Date: Wed, 31 Jan 2001 10:37:05 -0600
Cc: Steve Lord <lord@xxxxxxx>, David Wragg <dpw@xxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: Message from Marcelo Tosatti <marcelo@xxxxxxxxxxxxxxxx> of "Wed, 31 Jan 2001 12:34:46 -0200." <Pine.LNX.4.21.0101311233450.16763-100000@xxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
> On Wed, 31 Jan 2001, Steve Lord wrote:
> > 
> > OK, I see what is going on here - and I think this could actually
> > break regular XFS as well - if you use the loop device on a highmem
> > machine. I will fix it in my 2.4.1 merge which should be out in cvs
> > in a day or two. 2.4.1 is running with XFS, but I am not happy with
> > what the kernel changes have done to performance.
> Steve, 
> Could you please describe what performance problems are going on? 

It is difficult to nail down the cause yet, but dbench has taken a
significant hit (40%). Single file (bonnie) is comparable with 2.4.0, the
dbench issue may be related to the throttling being placed on the
ll_rw_block interface by Jens' changes. The problem with working out
a bottleneck in dbench is it is such a random pile of stuff that
you really cannot point a finger at any one thing. I need to go
find some more deterministic measurements.

The performance drop off is not limited to xfs though ext2 appears
to suffer as well.


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