I installed memcache module with separate memcached server.

But the load of web server(different than memcahed server) has doubled than before.

Is it normal? Is there a cpu-intensive job at memcache module?

Comments

robertdouglass’s picture

robertdouglass commented

That's interesting. We definitely need more benchmarks of all sorts, and the cases where I've needed to use memcache were all with the goal of reducing the load on the database server, so I wouldn't have noticed much if webserver load went up. Everyone is encouraged to do profiling... and all information helps. I don't have any guesses as to why you would be seeing this.

ksoonson’s picture

ksoonson commented

we have three servers: web server, db server, memcached server and after applying memcache, the load of db server was reduced.

I suspect searching for key value can increase the CPU load of web server but not quite sure.

I am also interested in other profiling result very much.

Shiny’s picture

Shiny commented

also check stats from memcache -- are you getting mostly misses, and not hits.

you cal also try tweaking the amount of memory allowed to memcache.

dkruglyak’s picture

dkruglyak commented

This could be caused by something else... Do you have php opcode cache installed? Is it properly configured?

I have APC installed and was wondering why page loads according to devel module were taking 26M on devel_init. Turned out I did not have enough shared memory allocated (apc.shm_size & apc.shm_segments) and on increasing it from 32M to 128M the memory consumption dropped to 2.5M and page load time got cut in half (to 2 seconds). Go figure.

Here are the APC settings documented: http://www.php.net/apc

slantview’s picture

slantview commented
Status: Active » Closed (fixed)
firebus’s picture

firebus commented

adding the memcache php extension will increase memory use per apache process.

if that exhausts your memory so that you start swapping out to disk, you'll see load increase - are you swapping?

i'm sure there's some CPU impact of running the php memcache extension, but i also have not noticed anything huge from it.

ifood’s picture

ifood commented

We recently implemented Memcache on our site www.ifood.tv and we are having the same problem. Apache load jumped significantly from 0.5-1 range to 10. We have Drupal 6.13 and we have multiple memcache bins setup. Our apc is in good shape and giving almost 100% hit. We noticed major increase in CPU utilization and Drupal sessions also jumped by several hundred.

Was your issue ever resolved. It will be helpful to learn what you guys did.

Any suggestion or comments is very much appreciated. Thanks for your help.