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From Gurpreet Singh <gurpreet.si...@gmail.com>
Subject Re: key_cache_size_in_mb
Date Fri, 29 Jun 2012 06:01:04 GMT
Vijay,
Thanks for the suggestion.
Row Key size is 8 bytes (its a long).
Is the issue here incorrect calculation really?
The server already had the key cache in memory when i stopped it, and it
was using abt 6 gigs of heap total. How is it tht it cannot startup again
with the same keycache?

/G


On Thu, Jun 28, 2012 at 4:25 PM, Vijay <vijay2win@gmail.com> wrote:

> > It has 13.7million keys
> How big is your Row Keys? Current calculation (in 1.1) assumes that the
> average size of the Entry<RowKey, Long> in the keycache is 16 bytes.
>
> One thing which you can do to get out this issue is to reduce the Keycache
> to a low enough to get the server started or increase the Heap to hold all
> the objects. (If you are using the visualVM try to see the object counts).
>
> Regards,
> </VJ>
>
>
>
>
> On Thu, Jun 28, 2012 at 3:40 PM, Gurpreet Singh <gurpreet.singh@gmail.com>wrote:
>
>> Vijay,
>> I am running into an issue right now, not sure if its related to this one.
>>
>> My cassandra 1.1 was running fine for a week, and the key cache size (as
>> checked by jconsole) increased to almost 650 mb. It has 13.7million keys. I
>> have set key_cache_size_in_mb to 800 mb. I checked the heap size, and it
>> was at 6 gigs. All good!
>> However, when i try to restart cassandra, it is unable to start now.
>> Before i shut it down, it seemed fine at 6 gigs, which means its able to
>> handle the memory requirements just fine. However it is not able to start
>> up anymore with the same key cache. jconsole says that the heap is full.
>>
>> Thanks
>> /G
>>
>>
>> On Thu, Jun 28, 2012 at 12:22 PM, Vijay <vijay2win@gmail.com> wrote:
>>
>>> in 1.1 we dont calculate the Key size accurately, hence we have the fix
>>> in https://issues.apache.org/jira/browse/CASSANDRA-4315
>>>
>>> Regards,
>>> </VJ>
>>>
>>>
>>>
>>>
>>> On Thu, Jun 28, 2012 at 11:25 AM, Gurpreet Singh <
>>> gurpreet.singh@gmail.com> wrote:
>>>
>>>> anyone have an explanation for this?
>>>> This kinda screws up memory calculations.
>>>>
>>>> /G
>>>>
>>>> On Mon, Jun 25, 2012 at 5:50 PM, Gurpreet Singh <
>>>> gurpreet.singh@gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>> I have a question about cassandra 1.1
>>>>>
>>>>> Just wanted to confirm if key_cache_size_in_mb is the maximum amount
>>>>> of memory that key cache will use in memory? If not, what is it?
>>>>>
>>>>> My observations:
>>>>> With key cache disabled, I started cassandra. I invoked Full GC
>>>>> through jconsole a couple of times just to make sure that memory is freed
>>>>> up.
>>>>> Total heap memory in use is 2.2 gigs. I have almost 550 million keys,
>>>>> so this looked reasonable as the bloom filter itself is around 1 gig.
>>>>>
>>>>> I enabled key cache again by making key_cache_size_in_mb to a value
>>>>> 800. This would lead cassandra to load a previously saved key cache file
of
>>>>> size 98 mb on disk. I restarted cassandra again. This time the heap size
>>>>> increased to 4.2 gigs. I checked the cache sizing in jconsole.
>>>>>
>>>>> KeyCacheCapacityInMb: 799
>>>>> KeyCacheSize: 410,316,048
>>>>>
>>>>> This says that the key cache size is 410 mb. However the increase in
>>>>> the heap is 2 gigs. Doesnt add up!!
>>>>>
>>>>> Can anyone explain this?
>>>>> Thanks
>>>>> Gurpreet
>>>>>
>>>>
>>>>
>>>
>>
>

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