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From "Fenghua Hu (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-10690) Optimize insertion/removal of replica in ShortCircuitCache.java
Date Fri, 29 Jul 2016 08:29:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15398939#comment-15398939
] 

Fenghua Hu edited comment on HDFS-10690 at 7/29/16 8:28 AM:
------------------------------------------------------------

Performance test result against hadoop-2.6.4:
Test configuration:
* 1 name node + 1 data node
* Datanode: 1 PCIe SSD, 1 SATA HDD, OS page cache: on, read ahead for PCIe SSD: 0
* Hbase 1.1.2
* Table: key: 10 bytes, value: 1KB, total table size: 320GB, region count: 30, storage policy:
ALL_SSD, blocksize: 8K
* YCSB 1.1.2, 4 clients, 16 processes / client, in total 64 processes

Test steps:
 Run GET queries with 64 YCSB processes for 30 minutes, record the QPS for each process。
Total QPS:
w/o patch: 95K
w/ patch: 135K

The performance gain is (135 - 95) / 95 = 42%.











was (Author: fenghua_hu):
Performance test result against hadoop-2.6.4:
Test configuration:
* 1 name node + 1 data node
* Datanode: 1 PCIe SSD, 1 SATA HDD, OS page cache: on, read ahead for PCIe SSD: 0
* Hbase 1.1.2
* Table: key: 10 bytes, value: 1KB, total table size: 320GB, region count: 30, storage policy:
ALL_SSD, blocksize: 8K
* YCSB 1.1.2, 4 clients, 16 processes / client, in total 64 processes

Test steps:
 Run GET queries with 64 YCSB processes for 30 minutes, record the QPS for each processes.
Total QPS:
w/o patch: 95K
w/ patch: 135K

The performance gain is (135 - 95) / 95 = 42%.










> Optimize insertion/removal of replica in ShortCircuitCache.java
> ---------------------------------------------------------------
>
>                 Key: HDFS-10690
>                 URL: https://issues.apache.org/jira/browse/HDFS-10690
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>    Affects Versions: 3.0.0-alpha2
>            Reporter: Fenghua Hu
>            Assignee: Fenghua Hu
>         Attachments: HDFS-10690.001.patch, HDFS-10690.002.patch
>
>   Original Estimate: 336h
>  Remaining Estimate: 336h
>
> Currently in ShortCircuitCache, two TreeMap objects are used to track the cached replicas.
> private final TreeMap<Long, ShortCircuitReplica> evictable = new TreeMap<>();
> private final TreeMap<Long, ShortCircuitReplica> evictableMmapped = new TreeMap<>();
> TreeMap employs Red-Black tree for sorting. This isn't an issue when using traditional
HDD. But when using high-performance SSD/PCIe Flash, the cost inserting/removing an entry
 becomes considerable.
> To mitigate it, we designed a new list-based for replica tracking.
> The list is a double-linked FIFO. FIFO is time-based, thus insertion is a very low cost
operation. On the other hand, list is not lookup-friendly. To address this issue, we introduce
two references into ShortCircuitReplica object.
> ShortCircuitReplica next = null;
> ShortCircuitReplica prev = null;
> In this way, lookup is not needed when removing a replica from the list. We only need
to modify its predecessor's and successor's references in the lists.
> Our tests showed up to 15-50% performance improvement when using PCIe flash as storage
media.
> The original patch is against 2.6.4, now I am porting to Hadoop trunk, and patch will
be posted soon.



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