mod_pagespeed uses too many threads -- in proportion to the number of vhosts

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mod_pagespeed crashes while stress testing using JMeter with 100 threads in the 
first 30 seconds. I increased the ULIMIT_MAX_FILES for user "nobody" but still 
not progress. 

Below are lines from the apache error log -
[Mon Aug 15 14:35:50 2011] [alert] [mod_pagespeed 0.9.17.7-716 @20399] 
[0815/143550:FATAL:net/instaweb/apache/serf_url_async_fetcher.cc(466)] Check 
failed: 0 == apr_thread_create(&thread_id_, __null, SerfThreadFn, this, pool_) 
(0 vs. 11)\nBacktrace:\n\t/etc/httpd/modules/mod_pagespeed.so(+0x36b1a) 
[0x7f66c5bd0b1a]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x24efa) 
[0x7f66c5bbeefa]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x38b6d) 
[0x7f66c5bd2b6d]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x34982) 
[0x7f66c5bce982]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x2b0e7) 
[0x7f66c5bc50e7]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9b33b) 
[0x7f66c5c3533b]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9a3d5) 
[0x7f66c5c343d5]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9a4fc) 
[0x7f66c5c344fc]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x23b24) 
[0x7f66c5bbdb24]\n\t/usr/sbin/httpd(ap_run_translate_name+0x68) 
[0x7f66d1f8a5e8]\n\t/usr/sbin/httpd(ap_process_request_internal+0x126) 
[0x7f66d1f8c7c6]\n\t/usr/sbin/httpd(ap_process_request+0x1b0) 
[0x7f66d1f9e790]\n\t/usr/sbin/httpd(+0x37668) 
[0x7f66d1f9b668]\n\t/usr/sbin/httpd(ap_run_process_connection+0x68) 
[0x7f66d1f97398]\n\t/usr/sbin/httpd(+0x3f097) 
[0x7f66d1fa3097]\n\t/usr/sbin/httpd(+0x3f3aa) 
[0x7f66d1fa33aa]\n\t/usr/sbin/httpd(ap_mpm_run+0xc1c) 
[0x7f66d1fa402c]\n\t/usr/sbin/httpd(main+0xb30) 
[0x7f66d1f7b840]\n\t/lib64/libc.so.6(__libc_start_main+0xfd) 
[0x7f66d04d3c5d]\n\t/usr/sbin/httpd(+0x16809) [0x7f66d1f7a809]
[Mon Aug 15 14:35:50 2011] [notice] child pid 20392 exit signal Aborted (6)
[Mon Aug 15 14:35:50 2011] [notice] child pid 20393 exit signal Aborted (6)
[Mon Aug 15 14:35:50 2011] [notice] child pid 20394 exit signal Aborted (6)
[Mon Aug 15 14:35:50 2011] [notice] child pid 20396 exit signal Aborted (6)
[Mon Aug 15 14:35:50 2011] [notice] child pid 20399 exit signal Aborted (6)
[Mon Aug 15 14:35:50 2011] [alert] [mod_pagespeed 0.9.17.7-716 @20397] 
[0815/143550:FATAL:net/instaweb/apache/serf_url_async_fetcher.cc(466)] Check 
failed: 0 == apr_thread_create(&thread_id_, __null, SerfThreadFn, this, pool_) 
(0 vs. 11)\nBacktrace:\n\t/etc/httpd/modules/mod_pagespeed.so(+0x36b1a) 
[0x7f66c5bd0b1a]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x24efa) 
[0x7f66c5bbeefa]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x38b6d) 
[0x7f66c5bd2b6d]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x34982) 
[0x7f66c5bce982]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x2b0e7) 
[0x7f66c5bc50e7]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9b33b) 
[0x7f66c5c3533b]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9a3d5) 
[0x7f66c5c343d5]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x9a4fc) 
[0x7f66c5c344fc]\n\t/etc/httpd/modules/mod_pagespeed.so(+0x23b24) 
[0x7f66c5bbdb24]\n\t/usr/sbin/httpd(ap_run_translate_name+0x68) 
[0x7f66d1f8a5e8]\n\t/usr/sbin/httpd(ap_process_request_internal+0x126) 
[0x7f66d1f8c7c6]\n\t/usr/sbin/httpd(ap_process_request+0x1b0) 
[0x7f66d1f9e790]\n\t/usr/sbin/httpd(+0x37668) 
[0x7f66d1f9b668]\n\t/usr/sbin/httpd(ap_run_process_connection+0x68) 
[0x7f66d1f97398]\n\t/usr/sbin/httpd(+0x3f097) 
[0x7f66d1fa3097]\n\t/usr/sbin/httpd(+0x3f3aa) 
[0x7f66d1fa33aa]\n\t/usr/sbin/httpd(ap_mpm_run+0xc1c) 
[0x7f66d1fa402c]\n\t/usr/sbin/httpd(main+0xb30) 
[0x7f66d1f7b840]\n\t/lib64/libc.so.6(__libc_start_main+0xfd) 
[0x7f66d04d3c5d]\n\t/usr/sbin/httpd(+0x16809) [0x7f66d1f7a809]

More Information
1. X-Mod-Pagespeed  0.9.17.7-716
2. Apache version 2.2.15
3. OS: Redhat Enterprise 6 running Linux 2.6.x (64 bit)

Original issue reported on code.google.com by haris...@gmail.com on 15 Aug 2011 at 9:42