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From Vijay <vijay2...@gmail.com>
Subject Re: key_cache_size_in_mb
Date Fri, 29 Jun 2012 18:22:34 GMT
You might want to show us the GC log's... if there are promotion failures,
count on the objects which you can get by inspecting the heapdumps etc, I
am kind of assuming stuff :)

Regards,
</VJ>



On Thu, Jun 28, 2012 at 11:01 PM, Gurpreet Singh
<gurpreet.singh@gmail.com>wrote:

> 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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