From: | Katsuhiko Okano <okano(dot)katsuhiko(at)oss(dot)ntt(dot)co(dot)jp> |
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To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: poor performance with Context Switch Storm at TPC-W. |
Date: | 2006-07-12 00:15:24 |
Message-ID: | 200607120915.ABF82340.TVuBOPLLULIPBPJ@oss.ntt.co.jp |
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Lists: | pgsql-hackers pgsql-patches |
hello.
> Do you have bgwriter on and what's the parameters? I read a theory somewhere
> that bgwriter scan a large portion of memory and cause L1/L2 thrushing, so
> with HT on, the other backends sharing the physical processor with it also
> get thrashed ... So try to turn bgwriter off or turn HT off see what's the
> difference.
bgwriter is ON.
at postgresql.conf:
> # - Background writer -
>
> bgwriter_delay = 200 # 10-10000 milliseconds between rounds
> bgwriter_lru_percent = 1.0 # 0-100% of LRU buffers scanned/round
> bgwriter_lru_maxpages = 5 # 0-1000 buffers max written/round
> bgwriter_all_percent = 0.333 # 0-100% of all buffers scanned/round
> bgwriter_all_maxpages = 5 # 0-1000 buffers max written/round
I tried turn H/T OFF, but CSStorm occurred.
Usually, CS is about 5000.
when CSStrom occurrence, CS is about 70000.
(CS is a value smaller than the case where H/T is ON.
I think that it is because the performance of CPU fell.)
Regards
--------
Katsuhiko Okano
okano katsuhiko _at_ oss ntt co jp
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