Re: Performance problem in aset.c

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jan Wieck <JanWieck(at)Yahoo(dot)com>, Karel Zak <zakkr(at)zf(dot)jcu(dot)cz>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Performance problem in aset.c
Date: 2000-07-12 13:12:04
Message-ID: 200007121312.JAA21029@candle.pha.pa.us
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> At 23:48 11/07/00 -0400, Tom Lane wrote:
> >Another idea is to split the returned chunk and put the wasted part back
> >as a smaller free chunk, but I don't think this solves the problem; it
> >just means that the wasted space ends up on a small-chunk freelist, not
> >that you can actually do anything with it. But maybe someone can figure
> >out a variant that works better.
>
> Can you maintain one free list for each power of 2 (which it might already
> be doing by the look of it), and always allocate the max size for the list.
> Then when you want a 10k chunk, you get a 16k chunk, but you know from the
> request size which list to go to, and anything on the list will satisfy the
> requirement.

Sounds like the BSD malloc memory manager. I can post details, or the
pages from a kernel book I have about it.

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