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:
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.
Previous Comments:
------------------------------------------------------------------------
[2010-01-21 23:16:42] ras...@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] ras...@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.
------------------------------------------------------------------------
[2009-09-03 15:06:28] olga at metacafe dot com
Thanks for the quick response.
We do work with APC. I tested the new PHP without APC also, to make sure
the fstat() calls aren't caused by it. But the statistics I sent to you
are from web server that works with APC.
You can also see from my first submission that in 5.2.9 fstat() doesn't
take much time.
------------------------------------------------------------------------
[2009-09-03 14:24:14] ras...@php.net
Still surprised these fstats take that long on your system. Note also
that if you install APC, they completely go away. If you are down to
caring about performance at the syscall level like that and you are not
running a decent opcode cache, you are kind of confused.
Here is a backtrace of those 3 fstats:
#1 0x0137642f in do_fstat ()
#2 0x0137768f in _php_stream_fopen ()
#3 0x013719ba in _php_stream_open_wrapper_ex ()
#4 0x0135a1a3 in php_stream_open_for_zend_ex ()
#5 0x0135a2e0 in php_stream_open_for_zend ()
#6 0x013ca05f in zend_stream_fixup ()
#7 0x01383ae7 in open_file_for_scanning ()
#8 0x01383c8d in compile_file ()
#9 0x011eb8f7 in phar_compile_file ()
#10 0x013b4fa7 in zend_execute_scripts ()
#11 0x0135be38 in php_execute_script ()
#1 0x0137642f in do_fstat ()
#2 0x01376ee1 in php_stdiop_stat ()
#3 0x0135a148 in php_zend_stream_fsizer ()
#4 0x0135a206 in php_stream_open_for_zend_ex ()
#5 0x0135a2e0 in php_stream_open_for_zend ()
#6 0x013ca05f in zend_stream_fixup ()
#7 0x01383ae7 in open_file_for_scanning ()
#8 0x01383c8d in compile_file ()
#9 0x011eb8f7 in phar_compile_file ()
#10 0x013b4fa7 in zend_execute_scripts ()
#11 0x0135be38 in php_execute_script ()
#1 0x0137642f in do_fstat ()
#2 0x01377189 in php_stdiop_set_option ()
#3 0x0136fc8e in _php_stream_set_option ()
#4 0x0137dcec in _php_stream_mmap_range ()
#5 0x0135a295 in php_stream_open_for_zend_ex ()
#6 0x0135a2e0 in php_stream_open_for_zend ()
#7 0x013ca05f in zend_stream_fixup ()
#8 0x01383ae7 in open_file_for_scanning ()
#9 0x01383c8d in compile_file ()
#10 0x011eb8f7 in phar_compile_file ()
#11 0x013b4fa7 in zend_execute_scripts ()
#12 0x0135be38 in php_execute_script ()
The do_fstat() function has a cache, but those 3 calls set the 'force'
flag to ignore the cached stat struct. We need to track down whether it
is possible to not force these. It seems like it should be possible to
get rid of at least one of those, if not 2.
But again, install an opcode cache, and this stops being a problem.
------------------------------------------------------------------------
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