Date: Tue, 13 Jul 1999 12:20:37 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Matthew Jacob <mjacob@feral.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Replacement for grep(1) (part 2) Message-ID: <199907131920.MAA80146@apollo.backplane.com> References: <Pine.BSF.4.05.9907131203350.9543-100000@semuta.feral.com>
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:> We could have the ability to mark processes as being more or less
:> preferable as kill candidates. I'm not sure I really care anymore,
:> though... there is so much disk space available now that it is fairly
:> difficult to run the system out of swap space. I don't think I've
:> run any of my personal systems out of swap space for at least a year
:
:I do this regularly and swap areas are difficult to configure sometimes.
:It would be desirable to have a growable swap vnode in ffs that you can
:set up in advance, or have a network nfs swap server for use in
:emergencies. This is a much better policy than killing processes, which is
:really microsoft style solution.
The basic problem with using file-backed swap is that swapping a page
out may require the temporary allocation of several pages - indirect
blocks for the file, resulting in possible low-memory deadlocks. That
said, I think that when the same problem with vnode-backed paging is
eventually solved, it will also cover file-backed swapping.
FreeBSD's swap subsystem has a basic limitation of 4 swap areas. This
is due to the design of the interleaving algorithms. Increasing this
number is simple, but it results in phenominally more kernel memory
getting wired. Within this limitation we can theoretically add and
remove swap areas with relative easy. It would be somewhat easier to do
under CURRENT because the swap metadata structures are simpler.
-Matt
Matthew Dillon
<dillon@backplane.com>
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