From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Idea: recycle WAL segments, don't delete/recreate 'em |
Date: | 2001-07-17 17:31:16 |
Message-ID: | 200107171731.f6HHVGx17673@candle.pha.pa.us |
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Lists: | pgsql-hackers |
> I have noticed that a large fraction of the I/O done by 7.1 is
> associated with initializing new segments of the WAL log for use.
> (We have to physically fill each segment with zeroes to ensure that
> the system has actually allocated a whole 16MB to it; otherwise we
> fall victim to the "hole-saving" allocation technique of most Unix
> filesystems.) I just had an idea about how to avoid this cost:
> why not recycle old log segments? At the point where the code
> currently deletes a no-longer-needed segment, just rename it to
> become the next created-in-advance segment.
This sounds good and with UNDO far off, would be a big win. The
segement number seems like a good idea. I can't see any disadvantages.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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