Re: [WIP PATCH] for Performance Improvement in Buffer Management

On Thu, Nov 22, 2012 at 2:05 PM, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:

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> >Sorry, I haven't followed this thread at all, but the numbers (43171 and
> 57920) in the last two runs of @mv-free-list for 32 clients look
> aberrations, no ? I wonder if *>*that's skewing the average.****
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> Yes, that is one of the main reasons, but in all runs this is consistent
> that for 32 clients or above this kind of numbers are observed.****
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> Even Jeff has pointed the similar thing in one of his mails and suggested
> to run the tests such that first test should run “with patch” and then
> “without patch”. ****
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> After doing what he suggested the observations are still similar.****
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Are we convinced that the jump that we are seeing is a real one then ? I'm
a bit surprised because it happens only with the patch and only for 32
clients. How would you explain that ?

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> > I also looked at the the Results.htm file down thread. There seem to be
> a steep degradation when the shared buffers are increased from 5GB to 10GB,
> both with and ****
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> > without the patch. Is that expected ? If so, isn't that worth
> investigating and possibly even fixing before we do anything else ?****
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> The reason for decrease in performance is that when shared buffers are
> increased from 5GB to 10GB, the I/O starts as after increasing it cannot
> hold all****
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> the data in OS buffers.
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Shouldn't that data be in the shared buffers if not the OS cache and hence
approximately same IO will be required ? Again, the drop in the performance
is so severe that it seems worth investigating that further, especially
because you can reproduce it reliably.

Thanks,
Pavan