Re: Wierd context-switching issue on Xeon - Mailing list pgsql-performance

From Tom Lane
Subject Re: Wierd context-switching issue on Xeon
Date
Msg-id 17856.1082598354@sss.pgh.pa.us
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In response to Re: Wierd context-switching issue on Xeon  (Josh Berkus <josh@agliodbs.com>)
List pgsql-performance
Kenneth Marshall <ktm@is.rice.edu> writes:
> If the context swap storm derives from LWLock contention, maybe using
> a random order to assign buffer locks in buf_init.c would prevent
> simple adjacency of buffer allocation to cause the storm.

Good try, but no cigar ;-).  The test cases I've been looking at take
only shared locks on the per-buffer locks, so that's not where the
context swaps are coming from.  The swaps have to be caused by the
BufMgrLock, because that's the only exclusive lock being taken.

I did try increasing the allocated size of the spinlocks to 128 bytes
to see if it would do anything.  It didn't ...

            regards, tom lane

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