[jira] [Work logged] (ARTEMIS-2317) Avoid long TTSP caused by Page::read using mmap read

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARTEMIS-2317?focusedWorklogId=231434&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-231434 ]

ASF GitHub Bot logged work on ARTEMIS-2317:
-------------------------------------------

                Author: ASF GitHub Bot
            Created on: 23/Apr/19 15:01
            Start Date: 23/Apr/19 15:01
    Worklog Time Spent: 10m 
      Work Description: franz1981 commented on pull request #2633: ARTEMIS-2317 Avoid long TTSP caused by Page::read using mmap read
URL: https://github.com/apache/activemq-artemis/pull/2633
 
 
   It implements Page::read using chunked reading of SequentialFile
   instead of using memory mapped files causing long time to safepoint
   issues.
 
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Issue Time Tracking
-------------------

            Worklog Id:     (was: 231434)
            Time Spent: 10m
    Remaining Estimate: 0h

> Avoid long TTSP caused by Page::read using mmap read
> ----------------------------------------------------
>
>                 Key: ARTEMIS-2317
>                 URL: https://issues.apache.org/jira/browse/ARTEMIS-2317
>             Project: ActiveMQ Artemis
>          Issue Type: Improvement
>            Reporter: Francesco Nigro
>            Priority: Major
>             Fix For: 2.7.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Page::read is using a readonly mmap to read paged messages: 
> if the OS mapped regions accessed are not into the OS page cache it can cause several major page faults that would lead to suffer very long time to safepoint pauses (it can be seen by enabling -XX:+PrintGCApplicationStoppedTime).
> Such pauses can delay significantly the GC work in a way similar to long Stop-Of-The-World pauses, blocking the broker long enough that any connected client will consider it dead or making the broker itself to suicide by shutdown.
> The original proposal to use mmap read has been used to avoid Page::read to allocate big direct ByteBuffers just to read entirely the paged messages from the filesystem: implementing chunked reading of those files while re-using the read ByteBuffer would allow to reduce the number of syscalls to read the file, avoiding the long time to safepoint pauses too.
> Any OS pauses on JNI (ie NIO FileChannel::read) won't cause any safepoint delay (ie JNI calls are IN a safepoint,not between).



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