Mark Kirkwood <[EMAIL PROTECTED]> writes:
> Shared Buffers Elapsed IO rate (from vmstat)
> -------------- ------- ---------------------
> 400MB 101 s 122 MB/s
> 2MB 100 s
> 1MB 97 s
> 768KB 93 s
> 512KB 86 s
> 256KB 77 s
> 128KB 74 s 166 MB/s
Hm, that seems to blow the "it's an L2 cache effect" theory out of the
water. If it were a cache effect then there should be a performance
cliff at the point where the cache size is exceeded. I see no such
cliff, in fact the middle part of the curve is darn near a straight
line on a log scale ...
So I'm back to asking what we're really measuring here. Buffer manager
inefficiency of some sort, but what? Have you tried oprofile?
regards, tom lane
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