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Re: LWLockRelease

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "pgsql-hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: LWLockRelease
Date: 2005-02-03 14:32:52
Message-ID: 15729.1107441172@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> A few thoughts on LWLock data structures...

> In lwlock.c we hold a list of lwlocks held:
> held_lwlocks[MAX_SIMUL_LWLOCKS]
> where
> #define MAX_SIMUL_LWLOCKS	100

> The code for LWLockRelease assumes that the last acquired lock will
> always be the first one to be released, and uses an O(N) loop to search
> for the lock to release.

> Setting MAX_SIMUL_LWLOCKS to this fairly high number doesn't seem to
> match the optimistic use of the O(N) algorithm.

So?  The search only examines the actually-in-use array entries.

			regards, tom lane

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