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Date:      Tue, 23 May 2006 17:17:57 +0300
From:      Giorgos Keramidas <keramida@ceid.upatras.gr>
To:        mlfbsd <mlfbsd@cognet.ci0.org>
Cc:        current@freebsd.org, Kris Kennaway <kris@obsecurity.org>
Subject:   Re: md /tmp and async mounts
Message-ID:  <20060523141757.GA2966@gothmog.pc>
In-Reply-To: <20060523143013.GA11472@ci0.org>
References:  <20060522211223.GA3621@xor.obsecurity.org> <20060522231437.GC1446@odin.ac.hmc.edu> <20060523133037.GA2908@gothmog.pc> <20060523143013.GA11472@ci0.org>

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On 2006-05-23 16:30, mlfbsd <mlfbsd@cognet.ci0.org> wrote:
>On Tue, May 23, 2006 at 04:30:37PM +0300, Giorgos Keramidas wrote:
>>On 2006-05-22 16:14, Brooks Davis <brooks@one-eyed-alien.net> wrote:
>>>On Mon, May 22, 2006 at 05:12:24PM -0400, Kris Kennaway wrote:
>>>> I noticed that with tmpmfs in rc.conf, the md is not being
>>>> mounted with -o async; this is an enormous performance
>>>> boost, so is there a reason it is not used, or just that it
>>>> was overlooked?
>>>
>>> Just overlooked as far as I know.  We correctly switched to
>>> not mounting with softupdates, but should probably switch to
>>> -o async.
>>
>> Right.  The only reasons why the current tmpmfs_flags doesn't
>> include the `-o async' option too are:
>>
>>     a) It didn't back when it was all hardcoded in the script
>>
>>     b) I didn't think about adding it by default when revision
>>        1.230 of src/etc/defaults/rc.conf was committed by me
>>
>> If it does improve things, we should probably make the change :)
>
> The sys/dev/md/md.c rev 1.115 commit log says async used to be
> the default, but was switched off because it was causing
> deadlocks. Did this get fixed since ?

I am not sure.  If a deadlock *does* exist though, then it's not
an improvement and we should definitely keep the default to its
current state until the bug is fixed.



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