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To: Anatol Belski <anatol.php@belski.net>, 'Dmitry Stogov' <dmitry@zend.com>
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Cc: 'Anatol Belski' <ab@php.net>, 'Kalle Sommer Nielsen' <kalle@php.net>,
 'Xinchen Hui' <xinchen.h@zend.com>, 'Nikita Popov' <nikita.ppv@gmail.com>,
 'Zeev Suraski' <zeev@zend.com>, 'Andi Gutmans' <andi@zend.com>,
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Date: Mon, 14 Sep 2015 18:31:29 -0700
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Subject: Re: [PHP-DEV] Re: [PHP-CVS] com php-src: Added an experemental
 ability to move PHP code pages (PHP TEXT segment) into HUGE pages. PHP should
 be configured and built with --enable-huge-code-pages, OS should be
 configured to provide huge pages. It's possibl
From: rasmus@lerdorf.com (Rasmus Lerdorf)

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On 09/14/2015 02:13 PM, Anatol Belski wrote:
>=20
>=20
>> -----Original Message-----
>> From: Dmitry Stogov [mailto:dmitry@zend.com]
>> Sent: Monday, September 14, 2015 10:37 PM
>> To: Anatol Belski <anatol.php@belski.net>
>> Cc: Anatol Belski <ab@php.net>; Kalle Sommer Nielsen <kalle@php.net>;
>> Rasmus Lerdorf <rasmus@lerdorf.com>; Xinchen Hui <xinchen.h@zend.com>;=

>> Nikita Popov <nikita.ppv@gmail.com>; Zeev Suraski <zeev@zend.com>; And=
i
>> Gutmans <andi@zend.com>; PHP Internals <internals@lists.php.net>
>> Subject: Re: [PHP-DEV] Re: [PHP-CVS] com php-src: Added an experementa=
l
>> ability to move PHP code pages (PHP TEXT segment) into HUGE pages. PHP=

>> should be configured and built with --enable-huge-code-pages, OS shoul=
d be
>> configured to provide huge pages. It's possibl
>>
>>>
>>> With the new huge memory pages feature I'd suggest a bit softer -
>>> enabling its building, but setting opcache.enable_huge_code_pages=3D0=
 by
>> default.
>>
>>
>> OK.
>>
>>
>>> Then it can be easy enable and give one more intermediate step for pr=
e
>>> testing and go into RC4 completely if ok.
>>
>>
>> In general we may get build problems on some platforms...
>>
>>
>>> What do you think?
>>>
>>
>> I didn't get, do you like to delay this for RC4? or enable it at compi=
le time and
>> disable at run-time by default for RC3?
>> I agree with both.
>>
> I was suggesting the latter - build and disable at run-time. With RC4 I=
 meant - as it's run-time enabled by default currently, that could be tur=
ned on by default in RC4 if everything was well in RC3.
>=20
> Regarding possible build issues you mention - probably some magic in co=
nfig.m4 could disable huge pages? I wasn't aware, but probably yep - like=
 FreeBSD or OSX likely to not to have the sys/prctl.h . This could be a r=
eason for delaying till RC4, but it's actually easy solved doing some tes=
t compilation in config.m4 . I'd see build + disable on run-time in RC3 a=
s a better move because it turns the test circle earlier which is good co=
nsidering there are only 4 RCs to go yet.

As long as we fail gracefully when compiled with hugepage support and
then run on a system that doesn't have any hugepages configured. These
days the build box and the production execution box are rarely the same
machine.

Redhat enables THP by default and has for a while, but I know lots of
admins that disable this feature right away on production machines. I
don't think it is default on Ubuntu, but at least they have hugepage
tools to make it easy to configure. And from a quick look at Debnian
(jessie) it wasn't obvious how to get hugepages working. I don't see a
package for hugeadm offhand. The kernel supports it, obviously, but you
need to take some steps to configure them.

Which means we also need to spend a bit of time documenting how to
enable hugepages at the OS level for the various operating systems to go
along with this feature.

-Rasmus


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