md /tmp and async mounts

[Giorgos Keramidas]

On 2006-05-23 16:30, mlfbsd <mlfbsd at 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 at 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.