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Date:      Mon, 11 Jun 2012 12:20:32 +0200
From:      Ivan Voras <ivoras@freebsd.org>
To:        freebsd-hackers@freebsd.org
Subject:   Re: SuperPages utilization survey
Message-ID:  <jr4gpg$5uf$2@dough.gmane.org>
In-Reply-To: <4FCFE714.6070502@FreeBSD.org>
References:  <jqac8f$6mn$1@dough.gmane.org> <1073159468.20120602121458@serebryakov.spb.ru> <4FC9D420.6010203@FreeBSD.org> <alpine.BSF.2.00.1206021054120.40882@wojtek.tensor.gdynia.pl> <4FC9D68D.60405@FreeBSD.org> <alpine.BSF.2.00.1206021228320.43360@wojtek.tensor.gdynia.pl> <CAF-QHFUhOF=aW5Y2LRByH5wi%2BKsezMyrZuUL0w0AQCNweEGTaA@mail.gmail.com> <4FC9FDBE.6080401@FreeBSD.org> <op.wffo7ogu34t2sn@tech304> <4FCFE714.6070502@FreeBSD.org>

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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@freebsd.org> w=
rote:
>>
>>> As far as i understand it does at least enable usage of pages up to 4=
MB,
>>> 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=
 =20
>> superpages we might be able to get a nice little performance boost wit=
h =20
>> little effort. Even the increase to 4MB for now is a welcome improveme=
nt. =20
>> I'll make sure to put this in my toolbox....
>=20
> 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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