Edit report at http://bugs.php.net/bug.php?id=49383&edit=1
ID: 49383
Comment by: a dot rogge at solvention dot de
Reported by: olga at metacafe dot com
Summary: Lots of empty fstat() calls slow performance
Status: Bogus
Type: Bug
Package: Performance problem
Operating System: Red Hat 3.4.6-10
PHP Version: 5.3, 6
Block user comment: N
New Comment:
First of all: No, we don't use open_basedir or safe_mode or stuff like
that.
But I still do not understand what this has to do with the issue.
The redundant fstat() calls are obviously *not* from open_basedir,
because the fstat() calls are done after the file was opened.
I run 5.1.6, 5.2.14 and 5.3.2 with the same configuration. For 5.1.6 and
5.2.14 everything looks normally, in 5.3.2 there are suddenly three
instead of one fstat() call after opening the file. The calls are
identical and adjacent with no other syscalls in between. The two
successive calls do not provide any more information than the first one
and thus are redundant and useless.
This is obviously a performance regression. Do you want to tell me that
this is a new feature?
Previous Comments:
------------------------------------------------------------------------
[2010-08-12 01:24:32] rasmus@php.net
Do you have openbase_dir enabled? If so, for security reasons we can't
use the
stat cache which is going to cause a lot of stats. For a setup with
slow stats, I
suggest chroot/jail or something along those lines rather than
open_basedir to
keep users separated.
------------------------------------------------------------------------
[2010-08-11 20:10:56] a dot rogge at solvention dot de
Nobody cares wether or not APC works around the problem. There is
obviously a regression from 5.2 to 5.3.
Somebody maanged to triple the number of fstat() calls that are done for
an include().
Yesterday I "reproduced" the issue on our webcluster. Running the Red
Hat provided PHP 5.1.6 (from RHEL 5.5) the loadavg was around 8 for all
boxes. Upgrading to PHP 5.3.2 made the loadavg raised to values of 30 or
higher. Page load time went from < 1 second to around 30 seconds.
The best part is: we did install and configure apc for 5.3.2, but not
for 5.1.6
So eventually 5.3.2 *with* APC produces 3 times more load and needs 30
times longer than our ancient 5.1.6 *without* APC.
However, I must admit that we have our PHP-files on GFS2 where stat() is
traditionally a bit slow.
------------------------------------------------------------------------
[2010-01-21 23:16:42] rasmus@php.net
Unable to reproduce under apc.
------------------------------------------------------------------------
[2009-10-14 11:28:06] olga at metacafe dot com
The problem persists.
We upgraded APC to the latest version (3.1.3p1). Cache full count is 0,
hit ratio is 99.9%. I understand that this shouldn't happen, but there
are still 3 fstat() calls per file opened.
Here's our APC configuration - maybe you can see if anything is wrong
with it? Do you have other versions?
apc.cache_by_default 1
apc.canonicalize 1
apc.coredump_unmap 0
apc.enable_cli 1
apc.enabled 1
apc.file_md5 0
apc.file_update_protection 2
apc.filters
apc.gc_ttl 3600
apc.include_once_override 1
apc.lazy_classes 0
apc.lazy_functions 0
apc.max_file_size 1M
apc.mmap_file_mask /tmp/apc.IR76ZW
apc.num_files_hint 1024
apc.preload_path
apc.report_autofilter 0
apc.rfc1867 0
apc.rfc1867_freq 0
apc.rfc1867_name APC_UPLOAD_PROGRESS
apc.rfc1867_prefix upload_
apc.rfc1867_ttl 3600
apc.shm_segments 1
apc.shm_size 128
apc.stat 0
apc.stat_ctime 0
apc.ttl 7200
apc.use_request_time 1
apc.user_entries_hint 4096
apc.user_ttl 7200
apc.write_lock 1
------------------------------------------------------------------------
[2009-09-03 16:49:18] rasmus@php.net
The only time this code is executed if you are running APC is if the
script is not cached. So, either your APC setup is not working, you are
constantly trashing your cache (check apc.php and look at the cache-full
counter), or something else weird is going on.
These fstats are coming from compiler which reads the script from disk
and compiles it down to opcodes. It is impossible for this code to
execute on an APC-cached script because we point the executor directly
at the already compiled opcodes in shared memory.
------------------------------------------------------------------------
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