memcached Digest, Vol 37, Issue 11

Roy Jay rj at
Tue Aug 7 12:08:11 UTC 2007


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Thank you,


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> Today's Topics:
>    1. Multiple eviction policies (Wojtek Meler)
>    2. about 2G memory problem and connection memory usage (Steve Chu)
> ----------------------------------------------------------------------
> Message: 1
> Date: Tue, 07 Aug 2007 11:21:27 +0200
> From: "Wojtek Meler" <wmeler at>
> Subject: Multiple eviction policies
> To: memcached <memcached at>
> Message-ID: <46b83997a6217 at>
> Content-Type: text/plain; charset=iso-8859-2
> Did you considered multiple eviction policies for memcached ?
> In common there are many types of data stored in cache and it would be 
> great if one could tune cache size and eviction policy for each type. I 
> know that it is possible to setup multiple memcached processes, but it 
> will be quite ineffective for thousands of caches.
> As far as I understand the code, current implementation has single hash 
> and linked list for LRU. It would be great if additional layer of hash 
> and linked list could be introduced that group data in caches, allowing 
> to set different eviction rules for each cache. I don't fully understand 
> "managed mode" but probably cache could be identified by part of data 
> key. Any comments ?
> Regards,
> Wojtek
> ------------------------------
> Message: 2
> Date: Tue, 7 Aug 2007 18:45:27 +0800
> From: "Steve Chu" <stvchu at>
> Subject: about 2G memory problem and connection memory usage
> To: memcached at
> Message-ID:
> 	<4ac0d28c0708070345q362a1ff3j3c2a7ea13c212a74 at>
> Content-Type: text/plain; charset=ISO-8859-1
> There is a limit that we only can do "-m 2048" in a 32bit box.
> Here's my situation:
> I dig into memcached's source code, and find that memcached is using
> malloc to get memory for connection structure, and slabs for
> items(objects). when we reach the 2G limit, so there's no more memory
> for connection structures available, and we can't connect mcd any
> more.
> Is there a need that we set "-m 1800", so we leave 248MB for
> connections. so, when the memcached reaches limit(here 1800) and
> starts to free items, we still can connect to it?
> Is -m option for slabs not for malloc?

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