Date: Wed, 10 Aug 2011 01:47:59 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Holger Kipp <Holger.Kipp@alogis.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, Daniel Kalchev <daniel@digsys.bg> Subject: Re: 32GB limit per swap device? Message-ID: <20110810084759.GA32346@icarus.home.lan> In-Reply-To: <CFE743A4-A5FA-4AC8-B090-E1174EB49473@alogis.com> References: <4E4143A6.6030307@digsys.bg> <20110809151646.GF1814@albert.catwhisker.org> <4E422F8A.1070508@digsys.bg> <20110810074759.GA30254@icarus.home.lan> <4E423CAC.20008@digsys.bg> <CFE743A4-A5FA-4AC8-B090-E1174EB49473@alogis.com>
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On Wed, Aug 10, 2011 at 08:27:27AM +0000, Holger Kipp wrote: > > Am 10.08.2011 um 10:09 schrieb Daniel Kalchev: > > > On 10.08.11 10:47, Jeremy Chadwick wrote: > >> On Wed, Aug 10, 2011 at 10:13:14AM +0300, Daniel Kalchev wrote: > >>> I am more concerned that with 32GB of swap in single device I could not dump kernel core, with 64GB of RAM. > >> My apologies if I've misunderstood something, but why does this of any > >> concern? Machine has 64GB RAM. You have a single swap slice that's > >> effectively 32GB. How is a kernel panic worth of 64GB RAM going to fit > >> into a 32GB swap slice? > >> > > The swap partitions are 64GB, it is only that FreeBSD refuses to use more than 32GB of each for swap. But.. it might happily dump core to the whole partition, tests will show. > > I doubt it. Have you tried increasing kern.maxswzone? It is the size in KB (for 32GB it is set to 33554432). > kern.maxswzone: Maximum memory for swap metadata The variable is set to 32MBytes, not 32GBytes. The default size is defined as variable VM_SWZONE_SIZE_MAX, which is 32*1024*1024 per sys/i386/include/param.h and sys/amd64/include/param.h. Furthermore, this variable does not do what you're implying. It's used within swap_pager_swap_init() in sys/vm/swap_pager.c, which is what's used for initialising a process that's being paged out (swapped out). That doesn't appear to have anything to do with actual memory dumps. So we're back to where we started: swap slices/partitions can be greater than 32GBytes in size, but "something" is limiting the maximum amount of memory which can be dumped to a single swap swap to 32GBytes. -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, US | | Making life hard for others since 1977. PGP 4BD6C0CB |
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