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Date:      Wed, 26 Dec 2007 21:13:32 +0100
From:      Uwe Doering <gemini@geminix.org>
To:        Mike Tancsa <mike@sentex.net>
Cc:        stable@freebsd.org
Subject:   Re: SMP on FreeBSD 6.x and 7.0: Worth doing?
Message-ID:  <4772B5EC.30807@geminix.org>
In-Reply-To: <200712261740.lBQHetRB061995@lava.sentex.ca>
References:  <200712220531.WAA09277@lariat.net> <476FBED0.2080400@samsco.org>	<200712241549.IAA19650@lariat.net> <476FDA10.4060107@samsco.org>	<200712241653.JAA20845@lariat.net> <476FE868.8080704@samsco.org>	<200712241723.lBOHNLtt049769@lava.sentex.ca>	<477252E4.4070707@samsco.org> <200712261740.lBQHetRB061995@lava.sentex.ca>

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Mike Tancsa wrote:
> At 08:11 AM 12/26/2007, Scott Long wrote:
>>>         How does one know if the vfs.ufs.dirhash_maxmem is set too 
>>> high and are exhausting KVA ?
>>
>> Panics, freezes, failure to exec new programs, failure to create 
>> pipes, etc.
> 
> Is there anyway to know ahead of time one is getting close to the stage 
> where all those "bad things" start to happen ?

At least on FreeBSD 4.11 you can do

   sysctl -a|grep kvm

and get something like this:

   vm.kvm_size: 1065353216
   vm.kvm_free: 348127232

Perhaps this works on later versions of FreeBSD, too.

Now, if vm.kvm_free drops to 10% or so of vm.kvm_size and continues to 
fall, and vfs.ufs.dirhash_mem still hasn't hit the 
vfs.ufs.dirhash_maxmem limit, it's time to get concerned.  Of course, 
you can also use the vm.kvm_* values to dimension vfs.ufs.dirhash_maxmem 
properly in the first place.

Regards,

    Uwe
-- 
Uwe Doering         |  EscapeBox - Managed On-Demand UNIX Servers
gemini@geminix.org  |  http://www.escapebox.net



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