Re: Block-level CRC checks

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: pgsql(at)mohawksoft(dot)com, "Aidan Van Dyk" <aidan(at)highrise(dot)ca>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, "Hannu Krosing" <hannu(at)2ndquadrant(dot)com>, "Decibel!" <decibel(at)decibel(dot)org>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-01 23:41:24
Message-ID: 10407.1222904484@sss.pgh.pa.us
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Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> a) You wouldn't have to keep the lock while doing the I/O.

Hoo, yeah, so the period of holding the share-lock could well be
*shorter* than it is now. Most especially so if the write() blocks
instead of just transferring the data to kernel space and returning.

I wonder whether that could mean that it's a win to double-buffer
even if we aren't computing a checksum? Nah, probably not.

regards, tom lane

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