[cifs-protocol] Re: [linux-cifs-client] Linux CIFS performance

Dave Kleikamp shaggy at linux.vnet.ibm.com
Wed Mar 7 19:11:35 GMT 2007

On Wed, 2007-03-07 at 12:41 -0600, Steve French wrote:
> After looking at a few posts complaining about Linux cifs performance
> vs. nfs, Shaggy and I looked at some traces, and Shaggy spotted
> something very important.   CIFS was rereading a page in one case in
> which it did not need to, and not marking a page up to date in one place
> (causing unnecessary i/o).   The result was a 20 to 30x improvement in
> iozone write/rewrite performance - it does not affect read performance
> or the other four write cases in iozone (or if so, not very much).
> This is a spectacular improvement in write performance.  I doubt that it
> would help the dd case mentioned in the earlier nfs related (since dd
> opens the file write only, and typically uses block sizes which are too
> small to be efficient).

Did you try dd?  Of the two things my patch does, the part I was trying
to fix was to address writes that were smaller than the page size and
beyond the end of the file.  I expect that to help dd with the small
block sizes.  The other fix for the bug I stumbled upon probably doesn't
affect dd performance.

I'll try to run a few tests myself.

David Kleikamp
IBM Linux Technology Center

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