Re: FreeBSD malloc.c, -lmalloc, and squid.

From: John S. Dyson <>
Date: Tue, 27 Aug 1996 12:34:40 -0500 (EST)

> Secondly, the sbrk()-based system recovery of memory assumes too
> much allocation locality: the recovery of memory (via sbrk() back
> to the system) can only occur at the end of the allocation region.
Actually, we have an madvise(2) in current that supports "freeing" pages, but
keeping the VM space. That doesn't do EXACTLY what you say above, but
it can help. I have been running with an augmented version of
phkmalloc with that change for a long time now.

> I would like to see an extention to the mmap() semantics for sparse
> reclaimation on a per-page basis: When a full page is no longer on
> use, it would be returned individually to the system.
You can do an munmap that does not correspond directly to an mmap. Also,
as I said above, we have an madvise(2) call (arg:MADV_FREE) that releases
the page, without giving up the vm space. Specifically, the page is
marked clean, and might/might-not be demand-zeroed the next time that you
use it.

Received on Tue Aug 27 1996 - 10:45:20 MDT

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