Re: accuracy of btt result on btreplay?

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Hi, Alan

It should be no changes on the system.

I compared the per io dump info, and found the merges did decrease a
lot. Another interesting thing I found from the blkparse output is the
write requests has much more "WS" (synchronous) flag in the replay
run.  Does the merges decrease due to the "S" flag?

Perhaps  I need to tune the "-max-pkts"? In my case, to increase its
value to let more requests have more opportunities to merge?

BTW. I also tried replaying "dd" traces, and found the number of
merges also decreases.

Thx, Xuekun

On Wed, Mar 3, 2010 at 10:05 PM, Alan D. Brunelle <Alan.Brunelle@xxxxxx> wrote:
>
> Hi Xuekun -
>
> Not sure why they Q2Q N value is down 5%, but the AVG Q2Q is pretty
> close - only 11msec (again, about 5%). After that, things are affected
> by merge rates most likely - note that there were 262882 merges on the
> first run whilst there were only 8970 on the second run. Perhaps you
> could look at the blkparse output from both and get a feel for the vast
> reduction in merges. [Any changes on the system between the runs?]
>
> Regards,
> Alan
>
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