Author: sandy
Date: Wed Oct 9 05:56:23 2013
New Revision: 1530500
URL: http://svn.apache.org/r1530500
Log:
YARN-976. Document the meaning of a virtual core. (Sandy Ryza)
Modified:
hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt
hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java
Modified: hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt
URL:
http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt?rev=1530500&r1=1530499&r2=1530500&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt (original)
+++ hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt Wed Oct 9 05:56:23 2013
@@ -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
Modified:
hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java
URL:
http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java?rev=1530500&r1=1530499&r2=1530500&view=diff
==============================================================================
---
hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java
(original)
+++
hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/api/records/Resource.java
Wed Oct 9 05:56:23 2013
@@ -28,7 +28,18 @@ import org.apache.hadoop.yarn.util.Recor
* <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 implement
/**
* 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 implement
/**
* 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
