From: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> |
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To: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> |
Cc: | Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PgHacker <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com> |
Subject: | Re: contrib/cache_scan (Re: What's needed for cache-only table scan?) |
Date: | 2014-03-12 06:43:18 |
Message-ID: | CAJrrPGcoJTof2bOW3SGzch0TrATt5WLmTi9cMAfub=k=BSsfiQ@mail.gmail.com |
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On Wed, Mar 12, 2014 at 5:26 PM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> Thanks for your efforts!
>> Head patched
>> Diff
>> Select - 500K 772ms 2659ms -200%
>> Insert - 400K 3429ms 1948ms 43% (I am
>> not sure how it improved in this case)
>> delete - 200K 2066ms 3978ms -92%
>> update - 200K 3915ms 5899ms -50%
>>
>> This patch shown how the custom scan can be used very well but coming to
>> patch as It is having some performance problem which needs to be
>> investigated.
>>
>> I attached the test script file used for the performance test.
>>
> First of all, it seems to me your test case has too small data set that
> allows to hold all the data in memory - briefly 500K of 200bytes record
> will consume about 100MB. Your configuration allocates 512MB of
> shared_buffer, and about 3GB of OS-level page cache is available.
> (Note that Linux uses free memory as disk cache adaptively.)
Thanks for the information and a small correction. The Total number of
records are 5 million.
The select operation is selecting 500K records. The total table size
is around 1GB.
Once I get your new patch re-based on the custom scan patch, I will
test the performance
again by increasing my database size more than the RAM size. And also
I will make sure
that memory available for disk cache is less.
Regards,
Hari Babu
Fujitsu Australia
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