Date: Wed, 10 Aug 2011 13:42:11 +0300 From: Daniel Kalchev <daniel@digsys.bg> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: 32GB limit per swap device? Message-ID: <4E426083.1020207@digsys.bg> In-Reply-To: <20110810084759.GA32346@icarus.home.lan> 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> <20110810084759.GA32346@icarus.home.lan>
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On 10.08.11 11:47, Jeremy Chadwick wrote: > 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. It seems there is still some confusion. Partition size(s) is 64GB, but FreeBSD will use only 32GB of that for swap. Trying: sysctl debug.minidump=0 sysctl debug.kdb.panic=1 Produces 64GB dump, but.. I can't see the dump on the swap device (savecore doesn't find the magic number). My swap device is gmirror or two slices (/dev/mirror/swap). Removing the gmirror and listing both slices for swap .. works. I could use separate device for dumps, but the disk real estate on this particular blade is limited... Well, I really asked two questions: Q1: Is FreeBSD still limited to 32GB per swap slice? A1: yes. There is limit set in /usr/src/sys/vm/swap_pager.c Q2: If FreeBSD will only use 32GB of the slice for swap, will it dump larger (64GB in my case) core in there? A2a: yes. A2b: If the swap slice is gmirrored, you don't get any dump back. I believe the gmirror bug might exist in smaller partitions as well, but haven't tested it yet (have few such systems that never duped core). It does not matter if I do full dump or minidump: on gmirrored 64GB partittion savecore does not find anything. Daniel
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