memory fragmentation issues in 1.2?

George Schlossnagle george at
Wed Dec 6 22:39:19 UTC 2006

Steven Grimm wrote:
> It's possible, but IMO unlikely, that this is memory fragmentation. What
> do your requests look like?

Mixed bag.  None are tiny - from the coule hundred bytes to couple K
range mostly.

 How many client connections are open at a
> time?


> Each client connection has some buffer space for incoming
> requests, and if you have a lot of clients that can add up to a fair bit
> of memory, especially if your application does very large multi-key
> "get" requests. 

I don't see how this would account for the monotonically growing aspect
of the behavior I'm seeing.  Shrinking my TCP buffers down is a good
idea though.

> Based on our experience that's what I'd say you're most
> likely running into; we see our memcached instances exceed their
> configured memory limits but it always stabilizes once they've reached a
> certain size.

Yeah... I would expect a swell as well, but they go from 800M -> 2G+,
which is more swell than I would like to see.

> That said, please try 1.2.1 and see if you see the same problem.



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