BRAINSTORMING NEEDED: Memcached Slowing Machine

[Don MacAskill]

On our database machines, we've had to disable swap entirely.  We did 
this naturally for memcached boxes without even benchmarking it.  You 
may want to try that on your memcached box.

I don't know how FreeBSD allocates memory these days, but lots of Linux 
distros prefer to swap out application data to keep a healthy disk cache 
available.  As you can imagine, this kills performance of things like 
memcached and even traditional disk-backed databases.

Don


Steven Grimm wrote:
> When the machine slows down, how much free physical memory does the 
> machine have? Is the entire memcached process memory-resident, or has 
> the OS started to swap it out? The instant memcached starts having to 
> swap, its performance plummets. The behavior you describe is consistent 
> with a memcached instance growing larger than the available physical 
> memory over time. When you restart it, it would start small again and 
> not need to swap.
> 
> -Steve
> 
> 
> Paul Boyes wrote:
>>
>> Hello,
>>
>>  
>>
>> I have posted a couple of related topics, but have not received many 
>> responses.  So, I thought I'd try again with a more general cry for help.
>>
>>  
>>
>> We have a FreeBSD server running a variety of php (web based) scripts 
>> that access/use memcached (latest version).   We have found  that the 
>> machine, after a period of time begins to slow down.   And, when we 
>> restart memcached it picks back up.  Any ideas you have as to why this 
>> might be happening would be greatly appreciated.  I will gladly 
>> provide more information if needed.  I am not sure what to provide 
>> though.  In genaral, I am would just like to know what might be 
>> causing thing or what might be happening.
>>
>>  
>>
>> Thanks,
>>
>>
>> Paul
>>
>>  
>>
>