[ 
https://issues.apache.org/jira/browse/CASSANDRA-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801496#comment-13801496
 ] 

Vijay edited comment on CASSANDRA-3578 at 10/22/13 5:28 AM:
------------------------------------------------------------

Found the bottleneck in the current!
Actually this happens during buffer.force()... CL.add queue is capped by 
commitlog_periodic_queue_size
{code}
public int commitlog_periodic_queue_size = 1024 * 
FBUtilities.getAvailableProcessors();
{code}

Hence, till we flush() (is called every 10 seconds) the writes to the CL is 
blocked. Hope that makes sense...


was (Author: vijay2...@yahoo.com):
Found the bottleneck in the current!
Actually this happens during buffer.force()... CL.add queue is capped by 
commitlog_periodic_queue_size
{code}
public int commitlog_periodic_queue_size = 1024 * 
FBUtilities.getAvailableProcessors();
{code}

Hence, till we flush() (is called every 10 seconds) the writes to the CL us 
blocked. Hope that makes sense...

> Multithreaded commitlog
> -----------------------
>
>                 Key: CASSANDRA-3578
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3578
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Vijay
>            Priority: Minor
>              Labels: performance
>         Attachments: 0001-CASSANDRA-3578.patch, ComitlogStress.java, 
> Current-CL.png, Multi-Threded-CL.png, parallel_commit_log_2.patch
>
>
> Brian Aker pointed out a while ago that allowing multiple threads to modify 
> the commitlog simultaneously (reserving space for each with a CAS first, the 
> way we do in the SlabAllocator.Region.allocate) can improve performance, 
> since you're not bottlenecking on a single thread to do all the copying and 
> CRC computation.
> Now that we use mmap'd CommitLog segments (CASSANDRA-3411) this becomes 
> doable.
> (moved from CASSANDRA-622, which was getting a bit muddled.)



--
This message was sent by Atlassian JIRA
(v6.1#6144)

Reply via email to