High server load - unserialize() taking up too much time?

[majidm]

Hey all,

We're experiencing pretty high load - we're hovering around 10-15 and every once in a while go into the 20s. I've installed APD and dumped a few pprof traces. _Consistently_, unserialize() is taking top spot with horrible execution times. Would anybody have any idea what I could do to improve that?

Examples:

Total Elapsed Time = 46.14
%Time (excl/cumm) (excl/cumm) (excl/cumm) Calls call s/call Memory Usage Name
--------------------------------------------------------------------------------------
38.8 26.65 26.65 0.67 0.67 0.05 0.05 20 0.0360 0.0360 0 unserialize


--
Total Elapsed Time = 26.83
%Time (excl/cumm) (excl/cumm) (excl/cumm) Calls call s/call Memory Usage Name
--------------------------------------------------------------------------------------
60.0 22.91 22.91 0.71 0.71 0.05 0.05 20 0.0380 0.0380 0 unserialize

-- and so on.

We're running PHP 5.2.4 and Apache 2.2.4 in prefork mode (both compiled, not RPM) on CentOS 4.4 32-bit.

I can provide the PHP / Apache compile configure strings if that's of any use. Running VB 3.6.4 on one site and 3.6.8 on the other.

Any help appreciated. Thanks very much!

-m