Date: Fri, 24 Aug 2012 17:10:01 -0700 From: Colin Percival <cperciva@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: alc@freebsd.org, =?UTF-8?B?RGFnLUVybGluZyBTbcO4cmdyYXY=?= <des@des.no>, freebsd-current@freebsd.org Subject: Re: Time to bump default VM_SWZONE_SIZE_MAX? Message-ID: <503817D9.3070006@freebsd.org> In-Reply-To: <201208241013.48805.jhb@freebsd.org> References: <502831B7.1080309@freebsd.org> <201208240748.19737.jhb@freebsd.org> <866288laq0.fsf@ds4.des.no> <201208241013.48805.jhb@freebsd.org>
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On 08/24/12 07:13, John Baldwin wrote: > On Friday, August 24, 2012 8:45:43 am Dag-Erling Smørgrav wrote: >> John Baldwin <jhb@freebsd.org> writes: >>> Note that on i386 you can't get more than 4GB of RAM without PAE, and if you >>> have any modern x86 box with > 4GB of RAM, you are most likely running amd64 >>> on it, not i386. I think i386 would be fine to just keep the limit it had. >> >> The limit we had was insufficient for 8 GB of swap. > > In absolute or practical terms? Not all swap blocks are fully utilized. At > Y! the install script we used would compute the maximum theoretical swap zone > needed and then cut it in half, and this worked quite well. Also, keep in mind, > this is for i386, not amd64. At this point i386 is going to be used on smaller > systems (e.g. netbooks, etc.), not servers that have lots of swap. I'd like to see i386 bumped slightly, just so that the rule of "allocate swap space equal to max(RAM, min(2*RAM, 8 GB))" (which I've seen in lots of places) is more likely to be safe. If I'm understanding things correctly, bumping from 32 MB up to 34.5 MB should give us a theoretical 16 GiB or a "safe" 8 GiB limit on swap usage (2^17 structures which are 276 bytes each on i386). But I agree that the real issue was with amd64, not i386. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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