Date: Tue, 02 Dec 2008 18:52:49 -0800 From: Kris Kennaway <kris@FreeBSD.org> To: Mike Tancsa <mike@sentex.net> Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-stable@freebsd.org Subject: Re: repeatable crash on RELENG7 Message-ID: <4935F481.6060407@FreeBSD.org> In-Reply-To: <200812021603.mB2G3eb9004481@lava.sentex.ca> References: <200812021319.mB2DJGJx003807@lava.sentex.ca> <20081202133812.GY3045@deviant.kiev.zoral.com.ua> <200812021412.mB2ECsEp004018@lava.sentex.ca> <20081202142045.GA3045@deviant.kiev.zoral.com.ua> <200812021603.mB2G3eb9004481@lava.sentex.ca>
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Mike Tancsa wrote:
> At 09:20 AM 12/2/2008, Kostik Belousov wrote:
>> On Tue, Dec 02, 2008 at 09:12:54AM -0500, Mike Tancsa wrote:
>> > At 08:38 AM 12/2/2008, Kostik Belousov wrote:
>> > >>
>> > >> mdconfig -a -t malloc -s 1800M
>> > >You cannot have ~ 2Gb of kernel memory allocated for md, at least
>> not on
>> > >i386.
>> >
>> > Thanks, how do I find out what the limit is on a machine ? Is it
>> > vm.kvm_size ?
>>
>> It is much less, and highly depends on your load, since KVA is used
>> for all
>> kind of allocations made by kernel. I think either md(4) or
>> mdconfig(8) have
>> a warning about malloc backing for md.
>
> Thanks! A warning might be helpful to prevent such foot shooting :)
malloc Storage for this type of memory disk is allocated
with
malloc(9). This limits the size to the malloc bucket
limit in the kernel. If the -o reserve option is not
set, creating and filling a large malloc-backed
memory
disk is a very easy way to panic a system.
You almost never want to use malloc backing for a md, in favour of swap
backing.
Kris
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