SuperPages utilization survey

[Ivan Voras]

On 07/06/2012 01:26, Florian Smeets wrote:
> On 05.06.12 16:29, Mark Felder wrote:
>> On Sat, 02 Jun 2012 06:49:18 -0500, Florian Smeets <flo at freebsd.org> wrote:
>>
>>> As far as i understand it does at least enable usage of pages up to 4MB,
>>> perhaps someone should teach mysql about the FreeBSD's limits?
>>> If you look at the output i sent, it certainly changes from using no
>>> superpage mappings at all to using them to some degree, if you script
>>> can be trusted
>>
>> Wow, this is a nice find. If someone were to add a patch for FreeBSD's  
>> superpages we might be able to get a nice little performance boost with  
>> little effort. Even the increase to 4MB for now is a welcome improvement.  
>> I'll make sure to put this in my toolbox....
> 
> I played with this some more. MySQL does not seem to use superpages.
> After a mysqld restart Ivan's script and procstat showed superpage
> mappings for mysqld, but it seems once MySQL "touches" the memory it's
> not in superpages anymore. I looked at the MySQL code a bit and one
> would need to add FreeBSD support in a couple of places. Perhaps I'll
> find some time to try this, but i cannot make any promises.

If I understand how superpages are promoted correctly, you may get a
nice effect simply by changing malloc()s of 2MB+ sizes to calloc()s.


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