On 24 February 2016 at 23:26, Amit Kapila <amit.kapil...@gmail.com> wrote:

> From past few weeks, we were facing some performance degradation in the
> read-only performance bench marks in high-end machines.  My colleague
> Mithun, has tried by reverting commit ac1d794 which seems to degrade the
> performance in HEAD on high-end m/c's as reported previously[1], but still
> we were getting degradation, then we have done some profiling to see what
> has caused it  and we found that it's mainly caused by spin lock when
> called via pin/unpin buffer and then we tried by reverting commit 6150a1b0
> which has recently changed the structures in that area and it turns out
> that reverting that patch, we don't see any degradation in performance.
> The important point to note is that the performance degradation doesn't
> occur every time, but if the tests are repeated twice or thrice, it
> is easily visible.

Not seen that on the original patch I posted. 6150a1b0 contains multiple
changes to the lwlock structures, one written by me, others by Andres.

Perhaps we should revert that patch and re-apply the various changes in
multiple commits so we can see the differences.

Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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