1MB entry size limit

Paolo Borelli paolo.borelli at gmail.com
Thu Apr 19 17:30:49 UTC 2007


Hi,

	sorry if this topic has already been discussed, but some googling
didn't yeld all the info I was looking for...

In the recent threads I read about the 1MB size limit of cache entries,
but I'd like to grow it for my usecase and I found some contradicting
information:

the top of slabs.c reads:

"The last slab size is always 1MB, since that's the maximum item size
allowed by the memcached protocol."

but in a mail from last year
(http://lists.danga.com/pipermail/memcached/2006-January/001879.html) I
read:

"You can recompile memcached with a higher POWER_LARGEST if you need
more than 1MB.  It's in slabs.c at the top.  Make it 21 to get 2MB max,
or 22 for 4MB max, etc"

so I was wondering two things:
1 - if the 1MB limit was just enforced by the slab allocator or if it
was a limit of the protocol
2 - If (as I hope) the limit is just in slabs.c, how should I change
POWER_LARGEST? Right now it is defined to 200, so I wonder if the bit I
quoted above is just a typo or if the code changed and other
modifications are needed...


Thanks in advance,

	Paolo



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