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YARN-976. Document the meaning of a virtual core. (Sandy Ryza) 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1530500 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Sanford Ryza 2013-10-09 05:56:23 +00:00
parent 5a87d89366
commit 00388655e5
2 changed files with 23 additions and 12 deletions
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2
hadoop-yarn-project/CHANGES.txt
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@ -57,6 +57,8 @@ Release 2.3.0 - UNRELEASED
YARN-465. fix coverage org.apache.hadoop.yarn.server.webproxy (Aleksey
Gorshkov and Andrey Klochkov via jlowe)
YARN-976. Document the meaning of a virtual core. (Sandy Ryza)
OPTIMIZATIONS
BUG FIXES

33
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java
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@ -28,7 +28,18 @@ import org.apache.hadoop.yarn.util.Records;
* <p><code>Resource</code> models a set of computer resources in the
* cluster.</p>
*
* <p>Currrently it only models <em>memory</em>.</p>
* <p>Currently it models both <em>memory</em> and <em>CPU</em>.</p>
*
* <p>The unit for memory is megabytes. CPU is modeled with virtual cores
* (vcores), a unit for expressing parallelism. A node's capacity should
* be configured with virtual cores equal to its number of physical cores. A
* container should be requested with the number of cores it can saturate, i.e.
* the average number of threads it expects to have runnable at a time.</p>
*
* <p>Virtual cores take integer values and thus currently CPU-scheduling is
* very coarse. A complementary axis for CPU requests that represents processing
* power will likely be added in the future to enable finer-grained resource
* configuration.</p>
*
* <p>Typically, applications request <code>Resource</code> of suitable
* capability to run their component tasks.</p>
@ -69,11 +80,10 @@ public abstract class Resource implements Comparable<Resource> {
/**
* Get <em>number of virtual cpu cores</em> of the resource.
*
* We refer to <em>virtual cores</em> to clarify that these represent
* <em>normalized</em> cores which may have a m:n relationship w.r.t
* physical cores available on the compute nodes. Furthermore, they also
* represent <em>idealized</em> cores since the cluster might be composed
* of <em>heterogenous</em> nodes.
* Virtual cores are a unit for expressing CPU parallelism. A node's capacity
* should be configured with virtual cores equal to its number of physical cores.
* A container should be requested with the number of cores it can saturate, i.e.
* the average number of threads it expects to have runnable at a time.
*
* @return <em>num of virtual cpu cores</em> of the resource
*/
@ -84,12 +94,11 @@ public abstract class Resource implements Comparable<Resource> {
/**
* Set <em>number of virtual cpu cores</em> of the resource.
*
* We refer to <em>virtual cores</em> to clarify that these represent
* <em>normalized</em> cores which may have a m:n relationship w.r.t
* physical cores available on the compute nodes. Furthermore, they also
* represent <em>idealized</em> cores since the cluster might be composed
* of <em>heterogenous</em> nodes.
*
* Virtual cores are a unit for expressing CPU parallelism. A node's capacity
* should be configured with virtual cores equal to its number of physical cores.
* A container should be requested with the number of cores it can saturate, i.e.
* the average number of threads it expects to have runnable at a time.
*
* @param vCores <em>number of virtual cpu cores</em> of the resource
*/
@Public