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@@ -721,7 +721,7 @@
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A TT ensures that a task is killed if it, and
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its descendants, use VMEM over the task's per-task limit. It also
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ensures that one or more tasks are killed if the sum total of VMEM
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- usage by all tasks, and their descendents, cross the node-limit.</p>
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+ usage by all tasks, and their descendants, cross the node-limit.</p>
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<p>Users can, optionally, specify the VMEM task-limit per job. If no
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such limit is provided, a default limit is used. A node-limit can be
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@@ -733,20 +733,25 @@
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<table>
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<tr><th>Name</th><th>Type</th><th>Description</th></tr>
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- <tr><td>mapred.tasktracker.vmem.reserved</td><td>long</td>
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- <td>A number, in bytes, that represents an offset. The total VMEM on
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- the machine, minus this offset, is the VMEM node-limit for all
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- tasks, and their descendants, spawned by the TT.
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+ <tr><td><code>mapred.cluster.map.memory.mb</code>, <code>mapred.cluster.reduce.memory.mb</code></td><td>long</td>
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+ <td>The size, in terms of virtual memory, of a single map/reduce slot
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+ in the Map-Reduce framework, used by the scheduler.
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+ A job can ask for multiple slots for a single task via
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+ mapred.job.map.memory.mb/mapred.job.reduce.memory.mb, up to the limit specified by
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+ mapred.cluster.max.map.memory.mb/mapred.cluster.max.reduce.memory.mb, if the scheduler supports the feature.
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+ The value of -1 indicates that this feature is turned off.
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</td></tr>
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- <tr><td>mapred.task.default.maxvmem</td><td>long</td>
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+ <tr><td><code>mapred.job.map.memory.mb</code>, <code>mapred.job.reduce.memory.mb</code></td><td>long</td>
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<td>A number, in bytes, that represents the default VMEM task-limit
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- associated with a task. Unless overridden by a job's setting,
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- this number defines the VMEM task-limit.
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+ associated with a map/reduce task. Unless overridden by a job's setting,
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+ this number defines the VMEM task-limit. These properties replace the old deprecated property,
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+ <code>mapred.task.default.maxvmem</code>.
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</td></tr>
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- <tr><td>mapred.task.limit.maxvmem</td><td>long</td>
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+ <tr><td><code>mapred.cluster.max.map.memory.mb</code>, <code>mapred.cluster.max.reduce.memory.mb</code></td><td>long</td>
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<td>A number, in bytes, that represents the upper VMEM task-limit
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- associated with a task. Users, when specifying a VMEM task-limit
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- for their tasks, should not specify a limit which exceeds this amount.
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+ associated with a map/reduce task. Users, when specifying a VMEM task-limit
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+ for their tasks, should not specify a limit which exceeds this amount. These properties replace the old deprecated property,
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+ <code>mapred.task.limit.maxvmem</code>.
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</td></tr>
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</table>
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@@ -754,7 +759,7 @@
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<table>
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<tr><th>Name</th><th>Type</th><th>Description</th></tr>
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- <tr><td>mapred.tasktracker.taskmemorymanager.monitoring-interval</td>
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+ <tr><td><code>mapred.tasktracker.taskmemorymanager.monitoring-interval</code></td>
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<td>long</td>
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<td>The time interval, in milliseconds, between which the TT
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checks for any memory violation. The default value is 5000 msec
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@@ -768,14 +773,6 @@
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above are missing or -1 is specified , memory monitoring is
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disabled for the TT.
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</li>
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- <li>In addition, monitoring is disabled if
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- <code>mapred.task.default.maxvmem</code> is greater than
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- <code>mapred.task.limit.maxvmem</code>.
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- </li>
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- <li>If a TT receives a task whose task-limit is set by the user
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- to a value larger than <code>mapred.task.limit.maxvmem</code>, it
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- logs a warning but executes the task.
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- </li>
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<li>Periodically, the TT checks the following:
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<ul>
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<li>If any task's current VMEM usage is greater than that task's
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@@ -786,7 +783,7 @@
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<li>If the sum total of VMEM used by all tasks and descendants is
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greater than the node-limit, the TT kills enough tasks, in the
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order of least progress made, till the overall VMEM usage falls
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- below the node-limt. Such killed tasks are not considered failed
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+ below the node-limit. Such killed tasks are not considered failed
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and their killing does not count towards the tasks' failure counts.
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</li>
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</ul>
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@@ -798,31 +795,15 @@
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tasks only if the TT has enough VMEM free. In addition, Schedulers may
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choose to consider the physical memory (RAM) available on the node
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as well. To enable Scheduler support, TTs report their memory settings
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- to the JobTracker in every heartbeat. Before getting into details,
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- consider the following additional memory-related parameters than can be
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- configured to enable better scheduling:</p>
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-
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- <table>
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- <tr><th>Name</th><th>Type</th><th>Description</th></tr>
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- <tr><td>mapred.tasktracker.pmem.reserved</td><td>int</td>
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- <td>A number, in bytes, that represents an offset. The total
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- physical memory (RAM) on the machine, minus this offset, is the
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- recommended RAM node-limit. The RAM node-limit is a hint to a
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- Scheduler to scheduler only so many tasks such that the sum
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- total of their RAM requirements does not exceed this limit.
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- RAM usage is not monitored by a TT.
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- </td></tr>
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- </table>
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+ to the JobTracker in every heartbeat.</p>
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<p>A TT reports the following memory-related numbers in every
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heartbeat:</p>
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<ul>
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<li>The total VMEM available on the node.</li>
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- <li>The value of <code>mapred.tasktracker.vmem.reserved</code>,
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- if set.</li>
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+ <li>The remaining VMEM available on the node.</li>
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<li>The total RAM available on the node.</li>
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- <li>The value of <code>mapred.tasktracker.pmem.reserved</code>,
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- if set.</li>
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+ <li>The remaining RAM available on the node.</li>
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</ul>
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</section>
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Thomas White