ID: 49383
Updated by: ras...@php.net
Reported By: olga at metacafe dot com
-Status: Assigned
+Status: Bogus
Bug Type: Performance problem
Operating System: Red Hat 3.4.6-10
PHP Version: 5.3, 6
Assigned To: rasmus
New Comment:
Unable to reproduce under apc.
Previous Comments:
------------------------------------------------------------------------
[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.
------------------------------------------------------------------------
[2009-09-03 12:59:44] olga at metacafe dot com
Turning all messages on/off didn't change the behavior. We tend
eliminate the notices on the development stage.
Can you please look at the system calls summary below? fstat() takes
25% of the total time. This doesn't happen in PHP 5.2.9.
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
24.85 33.820248 256 131908 fstat
13.54 18.431644 263 70002 66 lstat
9.81 13.346466 259 51520 mmap
9.72 13.223388 258 51175 munmap
9.39 12.775102 264 48450 192 stat
8.83 12.014341 265 45383 10 open
8.72 11.866944 257 46154 close
3.47 4.724639 255 18530 396 read
3.26 4.430927 256 17297 lseek
1.88 2.557480 244 10477 poll
1.59 2.170520 261 8326 recvfrom
1.52 2.073135 259 7994 sendto
...
------ ----------- ----------- --------- --------- ----------------
100.00 136.108580 526555 1324 total
In 5.2.9 fstat() takes about 8% of total time.
------------------------------------------------------------------------
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the rest of the comments, please view the bug report online at
http://bugs.php.net/49383
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