Self-tuning parameters

Igor Shmukler shmukler at
Thu Jul 15 10:16:12 PDT 2004

First thing to look at - statistics gathering code in vm_pageout.c.
It collects basic usage information upon which various decisions are made.
Then pageout thread basically does GCing based on memory pressure.
Used to be that depedning on pass number [vm_pageout(int pass)] system would either force or not force GC.
Logic is that is system recovered enough pages in one pass, pressure in not too high.
PS I am not 100% function names are accurate, but as far as I remember that's the basic idea.

-----Original Message-----
From: Avishay Traeger <atraeger at>
To: freebsd-hackers at
Date: Thu, 15 Jul 2004 12:51:22 -0400 (EDT)
Subject: Self-tuning parameters

> I am currently looking into how various operating systems self-tune their
> memory-related parameters (automatically adjusting parameters such as how
> much memory is allocated for various caches, buffer flushing rates, etc.).
> I have read a few posts indicating that FreeBSD self-tunes many of these
> parameters.  I was wondering if you could provide me with specific
> information (or point me at source code) about where and how FreeBSD does
> this.
> Thanks in advance,
> Avishay Traeger
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> freebsd-hackers at mailing list
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