| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Mark Cave-Ayland <m(dot)cave-ayland(at)webbased(dot)co(dot)uk>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Cost of XLogInsert CRC calculations |
| Date: | 2005-05-10 22:22:28 |
| Message-ID: | 27521.1115763748@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> The cause of the performance problem has been attributed to it being a
> 64-bit rather than 32-bit calculation. That is certainly part of it, but
> I have seen evidence that there is an Intel processor stall associated
> with the use of a single byte constant somewhere in the algorithm.
That's awfully vague --- can't you give any more detail?
I have seen XLogInsert eating significant amounts of time (up to 10% of
total CPU time) on non-Intel architectures, so I think that dropping
down to 32 bits is warranted in any case. But if you are correct then
that might not fix the problem on Intel machines. We need more info.
regards, tom lane
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