[Gllug] Painfully slow MySql performance on 64-bit Atom processor

[John Winters]

On 18/01/11 09:21, Nix wrote:
> On 13 Jan 2011, John Winters told this:
>> There are quite a few reports out there of performance problems using
>> 64-bit MySql on an ext4 partition.  The fix (?) is to mount the ext4
>> partition with the option "bound=0", which does indeed produce a
>> phenomenal performance improvement.  OTOH, I don't yet know what this
>> option actually does so I'm off to do some more reading.
>
> bound appears not to exist, from my quick grovel through the kernel
> source (at least, the string "bound" does not exist anywhere therein).

You're right - it's not "bound=0" it's "barrier=0".  It does produce a 
dramatic performance improvement.

I've since done some more reading and the essential difference 
apparently is that ext3 defaults to "barrier=0" and ext4 defaults to 
"barrier=1".  Still not quite sure what it means though.

> What you may want, if reliability is not a concern or your disk is
> battery-backed (or a laptop), is 'nobarrier'. Telling mysql not to sync
> may be worthwhile too.

How does one do that?

Cheers,
John
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