Date: Fri, 18 Dec 2015 17:19:33 +0300
From: Aleksander Alekseev <a.alekseev@postgrespro.ru>
To: Teodor Sigaev <teodor@sigaev.ru>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Amit Kapila
 <amit.kapila16@gmail.com>
Subject: Re: Patch: fix lock contention for HASHHDR.mutex
Message-ID: <20151218171933.500845f6@fujitsu>
In-Reply-To: <56740E41.4010708@sigaev.ru>
References: <20151211170001.78ded9d7@fujitsu>
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 <20151217151418.GB2224@awork2.anarazel.de>
 <20151217190342.07e4533a@fujitsu>
 <CA+Tgmob1-7=Bh21LyLXk7Yst1nzcA1P=rv0UKq1zH+A9PVehrg@mail.gmail.com>
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> Could we split one freelist in hash to NUM_LOCK_PARTITIONS freelists?
> Each partition will have its own freelist and if freelist is empty
> then partition should search an entry in freelists of other
> partitions. To prevent concurrent access it's needed to add one
> LWLock to hash, each partition should lock LWlock in share mode to
> work with its own freelist and exclusive to work with other freelists.
> 
> Actually, I'd like to improve all partitioned hashes instead of
> improve only one case.

It seems to be a most promising direction of research for now. I will
send a patch and benchmark results soon.


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