[infinispan-dev] Concurrent hashmaps parameters

[Manik Surtani]

On 16 Sep 2009, at 14:25, Mircea Markus wrote:

>
> On Sep 16, 2009, at 10:22 AM, Jason T. Greene wrote:
>
>> Bela Ban wrote:
>>>
>>> David M. Lloyd wrote:
>>>> NonBlockingHashMap is great *except* that it relies on
>>>> sun.misc.Unsafe,
>>>> which makes portability a bit iffy. I *think* that it could be
>>>> ported to
>>>> use Atomic* instead, but it looked like quite a bit of work to do
>>>> so (not
>>>> to mention testing).
>>>>
>>>> The problem with CHM is that they are *big*, so you don't want to
>>>> have a
>>>> lot of them - *especially* if you're using a high concurrency  
>>>> level,
>>>> because they get even bigger in that case.
>>>
>>> Understood that CHMs are big, but back to my question: how doesn
>>> Infinispan intend to address hashmaps with 1000 different keys ? Or
>>> are
>>> you guys already parameterizing creation of CHMs ?
>>>
>>
>> There is a concurrency level setting that the user can set based off
>> of
>> expected size (it also affects striping).
> I think this only has to do with the lock striping, and is rather
> related to the number of concurrent users expected to access the
> cache, not with the size of the data.
> AFAIK, there's no correlation between the number of cache entries, and
> the way the CHMs are being instantiated. Manik can put some more light
> on this on his return, but I do see a lot of sense for this  
> correlation.

Correct that this correlation between concurrency level and data  
container sizing is not there.  The CL is only used to tune the number  
of lock stripes in the LockManager.  All 3 container impls  
(SimpleDataContainer which uses CHMs and the FIFO/LRU containers that  
use custom concurrent map impls) could benefit from this.  Will create  
a JIRA to track this.

>> -- 
>> Jason T. Greene
>> JBoss, a division of Red Hat
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>
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--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org