When dealing with websites hosted on multiple webservers, having a common cache backend for storing optimized assets make sense.
PageSpeed offers support for using Memcached to make that possible.
A major benefit is that when webserver A has already crunched an image,
webserver B can pull the optimized image from the memcached server,
instead of having to redo the work.
Another benefit is reduced disk I/O as Memcached will take a lot of pressure away from PageSpeed's FileCache.
memcached -d installto install Memcached as a service
net start memcachedto start the Memcached service
To inform PageSpeed that Memcached is available for use, add a line like this to iispeed.config:
pagespeed MemcachedServers 127.0.0.1:11211
This assumes that Memcached is running on the same machine as the webserver, and is listening on its default port (11211). You can configure multiple memcached instances as well "host1:port1,host2:port2" to scale up.
Note that when using Memcached you must configure a file cache as well:
Enabling a file cache is done with a line like this in iispeed.config:
pagespeed FileCachePath c:\pscache\
That is basically it. If you added this configuration to the root iispeed.config file, these settings will inherit to all websites that have pagespeed enabled. Changes made to iispeed configuration files are applied immediately after saving.
By default Memcached will use up to 64MB of memory. To change how much RAM Memcached is allowed to use, follow these steps:
"C:\memcached\memcached.exe" -m 100 -d runserviceassigns 100MB
PS C:\memcached64> .\memcached.exe -h memcached 1.4.4-14-g9c660c0 -p <num> TCP port number to listen on (default: 11211) -U <num> UDP port number to listen on (default: 11211, 0 is off) -s <file> UNIX socket path to listen on (disables network support) -a <mask> access mask for UNIX socket, in octal (default: 0700) -l <ip_addr> interface to listen on (default: INADDR_ANY, all addresses) -s <file> unix socket path to listen on (disables network support) -a <mask> access mask for unix socket, in octal (default 0700) -l <ip_addr> interface to listen on, default is INADDR_ANY -d start tell memcached to start -d restart tell running memcached to do a graceful restart -d stop|shutdown tell running memcached to shutdown -d install install memcached service -d uninstall uninstall memcached service -r maximize core file limit -u <username> assume identity of
(only when run as root) -m <num> max memory to use for items in megabytes (default: 64 MB) -M return error on memory exhausted (rather than removing items) -c <num> max simultaneous connections (default: 1024) -k lock down all paged memory. Note that there is a limit on how much memory you may lock. Trying to allocate more than that would fail, so be sure you set the limit correctly for the user you started the daemon with (not for -u user; under sh this is done with 'ulimit -S -l NUM_KB'). -v verbose (print errors/warnings while in event loop) -vv very verbose (also print client commands/reponses) -vvv extremely verbose (also print internal state transitions) -h print this help and exit -i print memcached and libevent license -P <file> save PID in , only used with -d option -f <factor> chunk size growth factor (default: 1.25) -n <bytes> minimum space allocated for key+value+flags (default: 48) -L Try to use large memory pages (if available). Increasing the memory page size could reduce the number of TLB misses and improve the performance. In order to get large pages from the OS, memcached will allocate the total item-cache in one large chunk. -D <char> Use as the delimiter between key prefixes and IDs. This is used for per-prefix stats reporting. The default is ":" (colon). If this option is specified, stats collection is turned on automatically; if not, then it may be turned on by sending the "stats detail on" command to the server. -t <num> number of threads to use (default: 4) -R Maximum number of requests per event, limits the number of requests process for a given connection to prevent starvation (default: 20) -C Disable use of CAS -b Set the backlog queue limit (default: 1024) -B Binding protocol - one of ascii, binary, or auto (default) -I Override the size of each slab page. Adjusts max item size (default: 1mb, min: 1k, max: 128m)