first time user with out of memory question

timeless time at
Sun Jun 11 17:45:03 UTC 2006

Ivan Krstic wrote:

>Janning Vygen wrote:
>>and stats slab produced "out of memory" message, too. At this time it was 
>>impossible for many users to login to our web application.
>If memcached failure means your users can't log in, then you're using it
Janning is using the PHP Memcached session store. This is a fairly 
common way to use Memcached. It does have the side effect that if a 
session can't be created, the user can't log in.

I'm not convinced it's being used incorrectly. If a set() fails 
regularly on out-of-memory in *ANY* usage, nasty things will occur.

>>but i am concerned about it. As i have 3,5 GB dedicated to memached (-m 3584) 
>>it should not run out of memory.
>I recommend compiling a new binary from the Facebook branch; it contains
>a bunch of patches that generally make memcached saner.
Apparently the Facebook patches include a fix to this very type of 
problem, where even though you have more memory available to allocate, 
you can't allocate any slabs of the size you need, and so get the "out 
of memory" errors. Here we quote Steven Grimm:

    "I changed slabs.c so that it never gets those out-of-memory errors
    (at the cost of exceeding the maximum memory setting if you fill up
    your cache before you've allocated a slab of a particular class). "


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