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https://issues.apache.org/jira/browse/HDDS-15183?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ivan Andika reassigned HDDS-15183:
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Assignee: Ivan Andika
> Use POSIX fadvise for container replication
> -------------------------------------------
>
> Key: HDDS-15183
> URL: https://issues.apache.org/jira/browse/HDDS-15183
> Project: Apache Ozone
> Issue Type: Improvement
> Reporter: Ivan Andika
> Assignee: Ivan Andika
> Priority: Major
>
> This is simply an idea.
> Container replications currently still use buffered writes, meaning that it
> still occupies the page cache. This can cause page cache pollution which
> might trigger memory reclaim down the road, affecting performance. We can
> maybe achieve this by using DIRECT_IO, but currently we need to use
> TarContainerPacker which needs to be tar and untarred (since one container
> contains multiple blocks, unlike the proposal HDDS-12659 to put a single
> container in a single file). Therefore, we cannot use DIRECT_IO cleanly.
> We can consider using POSIX_FADV_DONTNEED
> (https://man7.org/linux/man-pages/man2/posix_fadvise.2.html) after container
> replication so that the OS can free this page caches immediately.
> Seems this is used by HDFS BlockSender and BlockReceiver so there is a
> precedent.
> Of course, we need to check whether the initial claim is correct and whether
> this is actually beneficial to prevent premature optimization. See
> https://github.com/restic/restic/issues/4465 for the possible issues.
> {code:java}
> import java.io.FileDescriptor;
> import org.apache.hadoop.io.nativeio.NativeIO;
> import org.apache.hadoop.io.nativeio.NativeIOException;
> private static void dontNeed(String identifier, FileDescriptor fd,
> long offset, long length) {
> try {
> NativeIO.POSIX.getCacheManipulator().posixFadviseIfPossible(
> identifier,
> fd,
> offset,
> length,
> NativeIO.POSIX.POSIX_FADV_DONTNEED);
> } catch (NativeIOException e) {
> LOG.debug("Failed to advise DONTNEED for {}", identifier, e);
> }
> }
> {code}
> {code:java}
> try (FileInputStream input = new FileInputStream(file)) {
> IOUtils.copy(input, output, bufferSize);
> dontNeed(file.getAbsolutePath(), input.getFD(), 0, 0);
> }
> {code}
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