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https://issues.apache.org/jira/browse/ARTEMIS-2317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16838551#comment-16838551
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ASF subversion and git services commented on ARTEMIS-2317:
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Commit 79465f7f88e32ca477655bb3f7fc6d261511ebae in activemq-artemis's branch
refs/heads/master from Francesco Nigro
[ https://gitbox.apache.org/repos/asf?p=activemq-artemis.git;h=79465f7 ]
ARTEMIS-2317 Reuse file buffer wrapper instances to reduce allocations
Page::read is allocating a new ChannelBufferWrapper on each
paged message read: to reduce the allocation rate, it could be
reused until a new wrapped ByteBuffer is created
> 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: 3h 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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