BRAINSTORMING NEEDED: Memcached Slowing Machine

Paul Boyes paul at
Tue Feb 27 00:01:17 UTC 2007

Thanks for the response.  I will run it by the system admin.



-----Original Message-----
From: Don MacAskill [mailto:don at] 
Sent: Monday, February 26, 2007 3:59 PM
To: Steven Grimm
Cc: Paul Boyes; memcached at
Subject: Re: BRAINSTORMING NEEDED: Memcached Slowing Machine

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.


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
> 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
>> 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
>> 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

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