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Date:      Wed, 06 Apr 2011 13:14:00 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Matthias Andree <matthias.andree@gmx.de>
Cc:        freebsd-stable@FreeBSD.org
Subject:   Re: Kernel memory leak in 8.2-PRERELEASE?
Message-ID:  <4D9C3CE8.5090201@FreeBSD.org>
In-Reply-To: <4D9B6178.7090809@gmx.de>
References:  <4D972FF7.6010901@acm.poly.edu>	<20110402153315.GP78089@deviant.kiev.zoral.com.ua>	<4D974393.80606@acm.poly.edu>	<4D9A307F.9070408@acm.poly.edu>	<20110404224334.GA64297@icarus.home.lan>	<4D9A68AA.6040803@acm.poly.edu>	<20110405010148.GA67821@icarus.home.lan>	<4D9B1E50.9020403@FreeBSD.org> <4D9B6178.7090809@gmx.de>

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on 05/04/2011 21:37 Matthias Andree said the following:
> Am 05.04.2011 15:51, schrieb Andriy Gapon:
> 
>> Boris,
>> ARC is an adaptive cache (as its name says), but the adaption doesn't happen
>> instantly.  So, when your applications do not use a lot of memory, but there is
>> steady filesystem usage, then ZFS ARC is going to gradually grow to consume an
>> optimum amount of RAM.  Then, your applications suddenly need a lot more memory,
>> they put pressure on VM system, ARC starts to shrink.  But if memory demand grows
>> faster than ARC shrinks, you are going to get a memory shortage.  And since you
>> don't have any swap to act as a safety net, you are getting out-of-memory situation.
>> So no surprises here, no system problems, just a normal foot-shooting :)
>>
>> Clamping maximum ARC size, as Jeremy has suggested, should help some.
>> Adding some swap would help a lot more.
> 
> The problem to me seems that ARC, the way you describe it, isn't really
> integrated with the system.

Define "really integrated".

> It's not buffer or cache memory, but some

True.

> separate application memory that can't adapt as quickly to system memory
> demands as all other kernel-managed caches and buffers can.

Other kernel-managed caches and buffers are not instant either.

But I have never compared "speed of adaptions".

-- 
Andriy Gapon



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