Have you taken into account the size of the bucket name? is it 12 bytes
for key+bucket?
Also there is some additional overhead that is due to memory alignment
requirements, depending on your CPU architecture.
I have done some tests on this for x86_64 a while ago:
size=55: overhead=9
size=56: overhead=8
size=57: overhead=23
size=58: overhead=22
size=59: overhead=21
size=60: overhead=20
size=61: overhead=19
size=62: overhead=18
size=63: overhead=17
size=64: overhead=16
size=65: overhead=15
size=66: overhead=14
size=67: overhead=13
size=68: overhead=12
size=69: overhead=11
size=70: overhead=10
size=71: overhead=9
size=72: overhead=8
Not much you can do about that, unless you want to use unaligned memory,
which is super complicated (replace malloc with your own allocator) and
has a huge performance penalty.
So lets assume your 12 bytes are include bucket and key:
43 byte overhead + 12 byte keydata = 55 bytes, this is the number of
bytes allocated per entry. In reality malloc(55) allocates 64 bytes
internally, so you total memory consumption is:
64byte*3*450Mio = 80 Gb
But if the bucket size is not included in the 12 bytes, and your bucket
name(s) has at least a size of 2 bytes we get:
(43 + 12 + 2) bytes = 57 bytes, and in this case malloc(57) really
allocates 80 bytes inernally. Therefore:
80byte*3*450Mio = 100Gb
Cheers,
Nico
Am 17.08.2011 19:43, schrieb Jacques:
So if my math is correct, consumption should be around 70-80 for me.
Yet we see a usage over 100. I'm also notclear what the step changes
are. If you have any insights on these that would be great. Thanks!
On Aug 17, 2011 12:07 AM, "Nico Meyer" <nico.me...@adition.com
<mailto:nico.me...@adition.com>> wrote:
> Hi Jacques,
>
> please read my reply back in May, which should clear things up:
>
>
http://lists.basho.com/pipermail/riak-users_lists.basho.com/2011-May/004292.html
>
> Cheers,
> Nico
>
> On 16.08.2011 21:09, Jacques wrote:
>> We're utilizing Riak 14.2 and we're seeing higher memory consumption
>> than we expect.
>>
>> We're running on a 4 node cluster with each node housing 32gb of memory
>> and are utilizing bitcask with a 3x write replication factor. We're
>> seeing faster growth than we expect and also seeing weird bounces
update.
>>
>> You can see an example chart <http://picturepush.com/public/6331935>.
>> (note, there are sometimes where we've had to stop the job for short
>> periods of time-- you can see these as flat spots).
>>
>> We are doing a large throttled import that has key sizes of
>> approximately 12 bytes. We're currently around 450mm unique items and
>> riak memory consumption is ~110gb. The input job is probably 95% new
>> puts and 5% overwriting puts.
>>
>> According to the capacity planner tools, our key space should probably
>> be about half what are actual memory consumption is.
>>
>> As you can see in the chart, we're also seeing jumps in memory size at
>> random intervals. What might these be? Nothing interesting in the logs
>> that I can see. Regular merges.
>>
>> A close up <http://picturepush.com/public/6332084> of a recent jump in
>> memory consumption for one of the nodes (they all look the same). There
>> are no corresponding distinct patterns within the cpu chart. Things are
>> pretty flat although we have more wait sometimes than we like (need
more
>> spindles clearly).
>>
>>
>> Any helpful thoughts?
>>
>> Thanks,
>> Jacques
>>
>>
>>
>>
>>
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