Subject: Re: Patch: fix lock contention for HASHHDR.mutex
To: Robert Haas <robertmhaas@gmail.com>,
 Aleksander Alekseev <a.alekseev@postgrespro.ru>
Cc: Andres Freund <andres@anarazel.de>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
References: <20151211170001.78ded9d7@fujitsu>
 <20151215122513.GC17724@alap3.anarazel.de>
 <CA+TgmoavsNuBNQf6ROn020F6g9gXJjtMrSkSFZ=RL1t2eJHQ5Q@mail.gmail.com>
 <20151217151418.GB2224@awork2.anarazel.de> <20151217190342.07e4533a@fujitsu>
 <CA+Tgmob1-7=Bh21LyLXk7Yst1nzcA1P=rv0UKq1zH+A9PVehrg@mail.gmail.com>
From: Teodor Sigaev <teodor@sigaev.ru>
Message-ID: <56740E41.4010708@sigaev.ru>
Date: Fri, 18 Dec 2015 16:46:41 +0300
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> Oh, that's an interesting idea.  I guess the problem is that if the
> freelist is unshared, then users might get an error that the lock
> table is full when some other partition still has elements remaining.

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.

-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                    WWW: http://www.sigaev.ru/


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