Date: Thu, 11 Feb 1999 03:23:07 -0500 (EST) From: "John S. Dyson" <dyson@iquest.net> To: mike@smith.net.au (Mike Smith) Cc: dyson@iquest.net, dg@root.com, tlambert@primenet.com, dillon@apollo.backplane.com, kuku@gilberto.physik.RWTH-Aachen.DE, hackers@FreeBSD.ORG Subject: Re: portability of shm, mmap, pipes and socket IPC Message-ID: <199902110823.DAA03550@y.dyson.net> In-Reply-To: <199902102350.PAA01211@dingo.cdrom.com> from Mike Smith at "Feb 10, 99 03:50:51 pm"
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Mike Smith said: > > David Greenman said: > > > >> >:The overall size of the shared memory segment is limited to that > > > >> >: which can fit in the kernels virtual address space; this > > > >> >: artificially restricts the maximum size. > > > >> > > > >> That isn't true and hasn't been true for several years in FreeBSD. > > > > > > > >Are you sure? > > > > > > Yes, I'm quite sure. > > > > > DG's statement is accurate. I removed that very artificial restriction over > > 2 yrs ago. There is no reason to use KVA space for data that the kernel never > > needs to see. Correcting that deficit was pretty much on my list as soon as > > I saw that problem when FreeBSD made it an official part of the distribution. > > Hmm, so does that mean that the shared memory pages can be paged out? > And if so, should we be removing the SHMMAXPGS kernel option (since our > current shared memory profile is woefully inadequate for most uses)? > Shared memory pages *can* be paged out. There are policy issues that DG and others (maybe including you) need to evaluate before deciding that SHMMAXPGS isn't something that is desirable. I suspect that SHMMAXPGS is pretty much redundant, but... :-). -- John | Never try to teach a pig to sing, dyson@iquest.net | it makes one look stupid jdyson@nc.com | and it irritates the pig. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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