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Date: Fri, 29 Jul 2016 08:29:20 +0000 (UTC)
From: "Fenghua Hu (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12992517.1469522930000.166717.1469780960908@Atlassian.JIRA>
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References: <JIRA.12992517.1469522930000@Atlassian.JIRA> <JIRA.12992517.1469522930868@arcas>
Subject: [jira] [Comment Edited] (HDFS-10690) Optimize insertion/removal of
 replica in ShortCircuitCache.java
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archived-at: Fri, 29 Jul 2016 08:29:23 -0000


    [ https://issues.apache.org/jira/browse/HDFS-10690?page=3Dcom.atlassian=
.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D1539=
8939#comment-15398939 ]=20

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=E3=80=82
Total QPS:
w/o patch: 95K
w/ patch: 135K

The performance gain is (135 - 95) / 95 =3D 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 =3D 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 =3D new TreeMa=
p<>();
> private final TreeMap<Long, ShortCircuitReplica> evictableMmapped =3D new=
 TreeMap<>();
> TreeMap employs Red-Black tree for sorting. This isn't an issue when usin=
g 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. T=
o address this issue, we introduce two references into ShortCircuitReplica =
object.
> ShortCircuitReplica next =3D null;
> ShortCircuitReplica prev =3D 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 fla=
sh as storage media.
> The original patch is against 2.6.4, now I am porting to Hadoop trunk, an=
d patch will be posted soon.


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