[Samba] performance regression between 30.14a and 3.0.20

Greg Dickie greg at max-t.com
Mon Apr 24 14:56:29 GMT 2006

Hey Jeremy,

Sorry, I'm at NAB in vegas and a little burned myself.... so we graph 
output from /proc/diskstats when we test. If I run a test with 3.0.21c 
the wio (field 7) and wblk (field 9) stats both show activity. This does 
not happen with 3.0.14a. eg: it appears that there is double the amount 
of write traffic.

Does that make any more sense?


Jeremy Allison wrote:
> On Sun, Apr 23, 2006 at 10:24:37PM -0400, Greg Dickie wrote:
>> Perhaps another data point that might ring a bell. While using 3.0.21c 
>> and monitoring direct IO vs. buffered IO (on XFS): if you see 40MBs of 
>> direct IO you will see another 40 MBs of buffered IO on 21c that you do 
>> not see on 14a. According to a colleague he saw this at one point in a 
>> previous revision and thought it was a problem of an extraneous sync 
>> somewhere.... This might explain why you don't see this with your ram disk.
> Ok, I don't understand this message :-). Can you explain exactly
> what you mean with "40 MBs of bufferd IO on 21c that you do not
> see on 14a" - how are you measuring this and where do you see it ?
> Use small words please, I'm very jet-lagged :-).
> Jeremy.

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