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https://issues.apache.org/jira/browse/HDFS-14356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16851647#comment-16851647
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Feilong He commented on HDFS-14356:
-----------------------------------
Thanks [~Sammi] a lot for your quite valuable comments.
{quote}1. typo "amd" in "Please refer to [http://pmem.io/] amd
[https://github.com/pmem/pmdk]";
{quote}
Yes, it's wrongly spelled. I will correct it.
{quote}2. "It is recommended to build the project with this option if user
plans to use SCM backed
HDFS cache." name the reason why it's recommended, "for better performance"?
{quote}
Yes, it would be clearer to user if we give specific reason for using PMDK.
{quote}3. for log the mapper block loader, try "this.class.getClass()" in super
class, instead of use instanceof sub class name.
{quote}
Good suggestion! Actually, the current impl is not friendly to code extension,
like adding a new subclass for PmemMappableBlockLoader.
{quote}4. if (!(cacheLoader instanceof NativePmemMappableBlockLoader))
{ return -1; }
{quote}
Another good suggestion! I will use interface design as you suggested to make
code clear logically in new patch.
{quote}5. Suggest change the log level to debug or trace.
LOG.info("Get InputStream by cache address.");
{quote}
Yes, the log level should be lowered to avoid complicating debugging.
{quote}6. several typo "pmemMappedAddres" in NativePmemMappedBlock
{quote}
I will correct this spelling issue.
{quote}7. 4 space indention for the second line. And double check other
functions too.
NativePmemMappedBlock(long pmemMappedAddres, long length,
ExtendedBlockId key) {
{quote}
I just noted the wrong indentions. I will correct the indention issue and check
other piece of code.
Thanks [~Sammi] again for your scrupulous review.
> Implement HDFS cache on SCM with native PMDK libs
> -------------------------------------------------
>
> Key: HDFS-14356
> URL: https://issues.apache.org/jira/browse/HDFS-14356
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: caching, datanode
> Reporter: Feilong He
> Assignee: Feilong He
> Priority: Major
> Attachments: HDFS-14356.000.patch, HDFS-14356.001.patch,
> HDFS-14356.002.patch, HDFS-14356.003.patch, HDFS-14356.004.patch,
> HDFS-14356.005.patch, HDFS-14356.006.patch
>
>
> In this implementation, native PMDK libs are used to map HDFS blocks to SCM.
> To use this implementation, user should build hadoop with PMDK libs by
> specifying a build option. This implementation is only supported on linux
> platform.
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