Tom Lane wrote:
> Hiroki Kataoka <kataoka@interwiz.jp> writes:
>
>>>>This small patch improves the performance of INSERT and UPDATE. By my
>>>>machine, these changes raised the performance about 5%~10% in pgbench.
>>>
>>>BTW, in profiling the backend I've never seen PageAddItem take more than
>>>about 1% of the runtime, and in pgbench in particular it seems to be
>>>down around 0.1% ... so the above seems a bit optimistic ...
>
>
>>I have the nearly same result, but pgbench says different. I don't know
>>why my test generates 5~10% performance improvement. Therefore, I want
>>to take a benchmark in a reliable environment.
>
>
> I've been testing this patch a bit, and I'm unable to measure any
> consistent improvement in pgbench times (sometimes it seems to win,
> and some other times it doesn't). And gprof still swears up and down
> that PageAddItem is only about 0.1% of the runtime, which would make
> it impossible to obtain more than an 0.1% speedup. I'm inclined to
> write off your result as measurement error --- it's notoriously hard
> to get reproducible results out of pgbench.
I played with the patch two weeks ago (pgbench and some bulkloading of
production data as well as restores from large dumps) - afair I have
been unable to measure any noticable real-life improvement.
Trusting pgbench is quite difficult for such tests - I can get easily up
to 15% variation on consecutive runs on my boxes here ...
Stefan