Date: Sun, 30 Sep 2001 13:22:23 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Alfred Perlstein <bright@mu.org> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, Vladimir Dozen <vladimir-dozen@mail.ru>, Wilko Bulte <wkb@freebie.xs4all.nl>, hackers@FreeBSD.ORG Subject: Re: VM: dynamic swap remapping (patch) Message-ID: <200109302022.f8UKMNi44948@earth.backplane.com> References: <909.1001839737@critter> <200109301959.f8UJxN544635@earth.backplane.com> <20010930150626.N59854@elvis.mu.org>
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:> :Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
:> :phk@FreeBSD.ORG | TCP/IP since RFC 956
:>
:> I think the file descriptor problem can be solved easily... simply
:> open the file, mmap() the entire 1G segment for this special application,
:> and then close() the file. Then have sbrk() just eats out of the mapped
:> segment. Alternatively sbrk() could open/mmap/close in large 1MB or 4MB
:> segments, again leaving no file descriptors dangling.
:
:Won't that cause fragmentation? You're forgettng the need to
:ftruncate or pre-zero the file unless that's been fixed.
:
:--
:-Alfred Perlstein [alfred@freebsd.org]
You have to pre-zero the file. You can do it in reasonably-sized
chunks (like 4M) without causing fragmentation. You *CANNOT* use
ftruncate() to extend the file - that will virtually guarentee massive
fragmentation.
-Matt
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