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Date: Fri, 6 Feb 2015 20:06:39 +0900
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To: Xinchen Hui <laruence@gmail.com>
Cc: Rasmus Lerdorf <rasmus@lerdorf.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Annotated PHP 5->7 extension diff
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Hi Xinchen,

On Fri, Feb 6, 2015 at 12:00 PM, Xinchen Hui <laruence@gmail.com> wrote:

> > On Feb 6, 2015, at 9:38 AM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:
> >
> > Hi Rasmus,
> >
> >> On Fri, Feb 6, 2015 at 7:28 AM, Rasmus Lerdorf <rasmus@lerdorf.com>
> wrote:
> >>
> >> Having just finished porting php-memcached (with help from Xinchen) to
> >> PHP7 I was wondering if it wouldn't be worthwhile to annotate the diff
> >> and explain why each change was made. The extension is complicated
> >> enough to cover most of the changes the bulk of extension authors need
> >> to worry about.
> >>
> >> The diff is easy enough to grab:
> >>
> >>  git clone https://github.com/php-memcached-dev/php-memcached.git
> >>  cd php-memcached
> >>  git checkout php7
> >>  git diff master php7
> >>
> >> It looks like this:
> >>
> >>  https://gist.github.com/anonymous/15cbc9947edb4f0a71fd
> >
> > It uses session save handler uses PS_MOD() which is legacy.
> > I may help to adopt PS_MOD_TIMESTAMP().
> > It eliminates writes and boost session performance a lot if apps
> > do not update session data always.
> >
> nice=EF=BC=8Cthanks
> btw did you bench your optimization on file handler against Wordpress?


No I don't, but I have some numbers.

https://github.com/php/php-src/pull/1016

-----------------------------------------------
I've tried to get some benchmarks. It seems current system is too fast to
get obvious performance difference.

Test command: ab -c 7 -n 500000 http://localhost:8888/session.php
Test script:

<?php
ini_set('session.save_path', '/home/tmp');
ini_set('session.lazy_write', 1); // Change mode here
ini_set('session.use_strict_mode', 0);

session_id('testid');
session_start(['read_and_close'=3D>0]); // Change mode here
//$_SESSION['test'] =3D ++$_SESSION['test'];
$_SESSION['a'] =3D str_repeat('a', 102400);
echo '<pre>';
var_dump(session_id(), $_SESSION['test']);


Old behavior was around 15000 reqs/sec.
"read_and_close" improved it to about 20000 reqs/sec. i.e 33% faster.
"lazy_write" did not improve # of reqs, but per process httpd disk writes
was reduced from 100 MB/s to 5 MB/s. i.e. There were 12 httpd processes,
1200 MB/s writes was reduced to 60 MB/s writes.

I think this would be good enough benchmark for merging.
-----------------------------------------------

As you can see, lazy_write didn't improve files much. The reason is my
current Linux
kernel already does lazy_write for files aren't changed. I'm using Fedora
21 x86_64.

However, per process writes are reduced from 1200MB/s to 60MB/s writes.
60MB/s
writes includes writes to log. This means network traffic will be reduced.
It should
help many apps use memcached save handler.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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