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Kernel CPU load on Apache/2.4.10 with SVN 1.8.10 (r1615264)

From: Charlie Smurthwaite <charlie_at_atechmedia.com>
Date: Wed, 17 Dec 2014 09:25:02 +0000

Hi,

I am running an SVN HTTP server using Apache/2.4.10 with SVN 1.8.10
(r1615264) and I am often seeing very high kernel CPU load.

The CPU time seems to be consumed in the kernel by "_raw_spin_lock",
with the httpd processes spending much of their time waiting on calls to
"futex".

Here's a syscall analysis from svn:
http://paste.codebasehq.com/pastes/7qzt68lx2eghz2gjns
Here's the kernel CPU time analysis: http://i.imgur.com/37Ryt5V.png
Here's a snapshot from htop showing why this is a problem:
http://i.imgur.com/I3mDDbi.png

I'd appreciate if anyone could tell me whether I have likely configured
something incorrectly, whether there is an obvious workaround, or
whether this needs to be escalated as a bug, and if so, to whom?

Thank you!

Charlie

My httpd is configured as follows:

root_at_storage02:~# /opt/subversion-server/bin/httpd -V
Server version: Apache/2.4.10 (Unix)
Server built: Nov 7 2014 15:16:58
Server's Module Magic Number: 20120211:36
Server loaded: APR 1.5.1, APR-UTIL 1.5.4
Compiled using: APR 1.5.1, APR-UTIL 1.5.4
Architecture: 64-bit
Server MPM: worker
   threaded: yes (fixed thread count)
     forked: yes (variable process count)
Server compiled with....
  -D APR_HAS_SENDFILE
  -D APR_HAS_MMAP
  -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
  -D APR_USE_SYSVSEM_SERIALIZE
  -D APR_USE_PTHREAD_SERIALIZE
  -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
  -D APR_HAS_OTHER_CHILD
  -D AP_HAVE_RELIABLE_PIPED_LOGS
  -D DYNAMIC_MODULE_LIMIT=256
  -D HTTPD_ROOT="/opt/subversion-server"
  -D SUEXEC_BIN="/opt/subversion-server/bin/suexec"
  -D DEFAULT_PIDLOG="logs/httpd.pid"
  -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
  -D DEFAULT_ERRORLOG="logs/error_log"
  -D AP_TYPES_CONFIG_FILE="conf/mime.types"
  -D SERVER_CONFIG_FILE="conf/httpd.conf"
Received on 2014-12-17 16:06:11 CET

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