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Re: mysterious dbench results

To: Thomas Graichen <thomas.graichen@xxxxxxxxxxxxxx>
Subject: Re: mysterious dbench results
From: Steve Lord <lord@xxxxxxx>
Date: Fri, 23 Feb 2001 16:54:11 -0600
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: Message from Thomas Graichen <news-innominate.list.sgi.xfs@xxxxxxxxxxxxx> of "23 Feb 2001 22:15:10 GMT." <news2mail-976nde$b2e$1@xxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
> Steve Lord <lord@xxxxxxx> wrote:
> 

> 
> ok - retried with those options (16384 in my case because 32k was
> too big for my small 700m test partition) and the dbench results
> got back to normal ... how about increasing those numbers by
> default a bit? - would there be any negative side-effects
> from doing so?

It is being looked into for internal sgi reasons too, yes the default
could be larger, it is just a matter of working out the numbers to use.

By the way, you can now use -o logbufs=8 at mount time, but this is
somewhat overkill.

> 
> > These should help XFS performance here, I suspect, but have not tried that
> > this will also help:
> 
> > echo 5000 > /proc/sys/vm/pagebuf/flush_int
> 
> > This will make the interval between dirtying file data and flushing it to
> > disk closer to that used by ext2. One of the issues with dbench is files
> > getting removed shortly after they are created, you can get mush better
> > performance if the removal happens before the data goes out to disk.
> 
> will try this too now

This will not really help - I tried it.

Other changes coming down the pipeline - probably next week will help too,
we have better dbench and bonnie numbers on some internal code right now.

Steve



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