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Re: LWLock cache line alignment

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: LWLock cache line alignment
Date: 2005-02-03 16:02:49
Message-ID: 16463.1107446569@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
>> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] wrote
>> I've looked at this before and I think it's a nonstarter;
>> increasing the
>> size of a spinlock to 128 bytes is just not reasonable.

> Well, the performance is unreasonably poor, so its time to do something,
> which might if it is unreasonable for the general case would need to be
> port specific.

Well, it might be worth allocating a full 128 bytes just for the fixed
LWLocks (BufMgrLock and friends) and skimping on the per-buffer locks,
which should be seeing far less contention than the fixed locks anyway.
But first lets see some evidence that this actually helps?

			regards, tom lane

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