incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Robert Coli <rc...@digg.com>
Subject Re: Calculate memory used for keycache
Date Tue, 15 Mar 2011 03:46:23 GMT
On Mon, Mar 14, 2011 at 1:19 PM, Peter Schuller
<peter.schuller@infidyne.com> wrote:
>> How is it possible calculate this value? I think that key size, if we use
>> RandomPartitioner will 16 bytes so keycache will took 16*(num of keycache
>> elements) bytes ??
>
> The easiest way right now is probably empirical testing. The issue is
> that the "memory use" must include overhead associated with the data
> structures involved, as well as longer-term effects like fragmentation
> in old-space in the GC (similarly to malloc/free).

In 0.7 and trunk, there is "nodetool clear[row|key]cache", so your
testing could be of the form :

a) start cluster
b) read enough keys to populate your caches per CF
c) measure memory usage
d) clear cache
e) measure memory usage

=Rob

Mime
View raw message