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Date: Mon, 18 Feb 2013 16:03:26 -0500
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To: Rasmus Lerdorf <rasmus@lerdorf.com>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] PHP causing high number of NFS getattr operations?
From: brendon@newgrounds.com (Brendon Colby)

On Mon, Feb 18, 2013 at 3:35 PM, Rasmus Lerdorf <rasmus@lerdorf.com> wrote:
> On 02/18/2013 12:26 PM, Brendon Colby wrote:
>
>> Rasmus said:
> Wow, people are still serving web files over NFS? Sounds painful.
>
> But, this is what APC's apc.include_once_override setting tries to
> address. Try turning that on.

Yep - I think it would be a lot more painful if we didn't use a very
expensive NetApp Filer to serve NFS (the solution before the Filer
would lock up every few weeks). I'm really surprised more people
haven't complained about this. I've seen a few complaints about people
seeing poor PHP app performance on NFS, but they usually move to
gluster or something else before ever figuring it out. Maybe very few
people use NFS to serve web files - who knows.

I tried apc.include_once_override - no change. I set up Apache to one
process and straced it. I clicked around on the site a few times and
see the typical pattern:

open("[PATH]/CacheFile.class.php", O_RDONLY) = 10
fstat(10, {st_mode=S_IFREG|0664, st_size=2097, ...}) = 0
fstat(10, {st_mode=S_IFREG|0664, st_size=2097, ...}) = 0
fstat(10, {st_mode=S_IFREG|0664, st_size=2097, ...}) = 0

Out of 486 open() calls, 263 were for PHP files (54%). Here is my
current APC config:

extension=/usr/local/lib/php/extensions/apc.so
apc.enabled=1
apc.shm_segments=1
apc.optimization=0
apc.shm_size=256M
apc.ttl=1200
apc.user_ttl=1200
apc.num_files_hint=300
apc.mmap_file_mask=/apc.shm.XXXXXX
apc.slam_defense=0
apc.write_lock=1
apc.include_once_override=1

apc.stat=0 doesn't help. Every PHP request causes an open() and
subsequent getattr() to the Filer no matter what options I set.