[
https://issues.apache.org/jira/browse/HDFS-12911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16291410#comment-16291410
]
Uma Maheswara Rao G commented on HDFS-12911:
--------------------------------------------
[~anu],
>if we are pulling this out of NN, wouldn't this be a no-op?
If I understand the discussions correctly, all participants not ok to pull out,
considering the overheads than keeping inside.
Considering the facts that:
1. With disable of SPS, absolutely no effect on NN, I have posted benchmarks.
2. Front Q filing up is not real issue, as that is not going to be too much
memory consumption with realistic scenarios. To increase the speed of
processing, we have to tune DN bandwidths, but not NN Qs. So, with throttling,
processing memory will be constant.
3. It will be easy to respect replication tasks as high priority tasks if we
are inside Hadoop via keeping inline tasks controlling via xmits.
4. Non of the tools like, Balancer/DiskBalancer, need to track or access
namespace, they just need utilization and DN block informations. So, this is
not exactly same as that.
5. We did not get consensus to add new process yet.
6. We got comments from other reviewer about lock and other stuff, respecting
their reviews, we are continuing to do this task. We can continue discussions
in HDFS-10285 if further issues.
> [SPS]: Fix review comments from discussions in HDFS-10285
> ---------------------------------------------------------
>
> Key: HDFS-12911
> URL: https://issues.apache.org/jira/browse/HDFS-12911
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Reporter: Uma Maheswara Rao G
> Assignee: Rakesh R
> Attachments: HDFS-12911.00.patch
>
>
> This is the JIRA for tracking the possible improvements or issues discussed
> in main JIRA
> So far comments to handle
> Daryn:
> # Lock should not kept while executing placement policy.
> # While starting up the NN, SPS Xattrs checks happen even if feature
> disabled. This could potentially impact the startup speed.
> UMA:
> # I am adding one more possible improvement to reduce Xattr objects
> significantly.
> SPS Xattr is constant object. So, we create one Xattr deduplication object
> once statically and use the same object reference when required to add SPS
> Xattr to Inode. So, here additional bytes required for storing SPS Xattr
> would turn to same as single object ref ( i.e 4 bytes in 32 bit). So Xattr
> overhead should come down significantly IMO. Lets explore the feasibility on
> this option.
> Xattr list Future will not be specially created for SPS, that list would have
> been created by SetStoragePolicy already on the same directory. So, no extra
> Feature creation because of SPS alone.
> # Currently SPS putting long id objects in Q for tracking SPS called Inodes.
> So, it is additional created and size of it would be (obj ref + value) = (8 +
> 8) bytes [ ignoring alignment for time being]
> So, the possible improvement here is, instead of creating new Long obj, we
> can keep existing inode object for tracking. Advantage is, Inode object
> already maintained in NN, so no new object creation is needed. So, we just
> need to maintain one obj ref. Above two points should significantly reduce
> the memory requirements of SPS. So, for SPS call: 8bytes for called inode
> tracking + 8 bytes for Xattr ref.
> # Use LightWeightLinkedSet instead of using LinkedList for from Q. This will
> reduce unnecessary Node creations inside LinkedList.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
