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ASF subversion and git services commented on IMPALA-12980: ---------------------------------------------------------- Commit 6abfdbc56c3d0ec3ac201dd4b8c2c35656d24eaf in impala's branch refs/heads/master from Riza Suminto [ https://gitbox.apache.org/repos/asf?p=impala.git;h=6abfdbc56 ] IMPALA-12980: Translate CpuAsk into admission control slots Impala has a concept of "admission control slots" - the amount of parallelism that should be allowed on an Impala daemon. This defaults to the number of processors per executor and can be overridden with -–admission_control_slots flag. Admission control slot accounting is described in IMPALA-8998. It computes 'slots_to_use' for each backend based on the maximum number of instances of any fragment on that backend. This can lead to slot underestimation and query overadmission. For example, assume an executor node with 48 CPU cores and configured with -–admission_control_slots=48. It is assigned 4 non-blocking query fragments, each has 12 instances scheduled in this executor. IMPALA-8998 algorithm will request the max instance (12) slots rather than the sum of all non-blocking fragment instances (48). With the 36 remaining slots free, the executor can still admit another fragment from a different query but will potentially have CPU contention with the one that is currently running. When COMPUTE_PROCESSING_COST is enabled, Planner will generate a CpuAsk number that represents the cpu requirement of that query over a particular executor group set. This number is an estimation of the largest number of query fragment instances that can run in parallel without waiting, given by the blocking operator analysis. Therefore, the fragment trace that sums into that CpuAsk number can be translated into 'slots_to_use' as well, which will be a closer resemblance of maximum parallel execution of fragment instances. This patch adds a new query option called SLOT_COUNT_STRATEGY to control which admission control slot accounting to use. There are two possible values: - LARGEST_FRAGMENT, which is the original algorithm from IMPALA-8998. This is still the default value for the SLOT_COUNT_STRATEGY option. - PLANNER_CPU_ASK, which will follow the fragment trace that contributes towards CpuAsk number. This strategy will schedule more or equal admission control slots than the LARGEST_FRAGMENT strategy. To do the PLANNER_CPU_ASK strategy, the Planner will mark fragments that contribute to CpuAsk as dominant fragments. It also passes max_slot_per_executor information that it knows about the executor group set to the scheduler. AvgAdmissionSlotsPerExecutor counter is added to describe what Planner thinks the average 'slots_to_use' per backend will be, which follows this formula: AvgAdmissionSlotsPerExecutor = ceil(CpuAsk / num_executors) Actual 'slots_to_use' in each backend may differ than AvgAdmissionSlotsPerExecutor, depending on what is scheduled on that backend. 'slots_to_use' will be shown as 'AdmissionSlots' counter under each executor profile node. Testing: - Update test_executors.py with AvgAdmissionSlotsPerExecutor assertion. - Pass test_tpcds_queries.py::TestTpcdsQueryWithProcessingCost. - Add EE test test_processing_cost.py. - Add FE test PlannerTest#testProcessingCostPlanAdmissionSlots. Change-Id: I338ca96555bfe8d07afce0320b3688a0861663f2 Reviewed-on: http://gerrit.cloudera.org:8080/21257 Reviewed-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com> > Translate CpuAsk into admission control slot to use > --------------------------------------------------- > > Key: IMPALA-12980 > URL: https://issues.apache.org/jira/browse/IMPALA-12980 > Project: IMPALA > Issue Type: Improvement > Components: Distributed Exec, Frontend > Reporter: Riza Suminto > Assignee: Riza Suminto > Priority: Major > > Admission control slot accounting is described in IMPALA-8998. On each > backend, number of. It compute 'slots_to_use' for each backend based on the > max number of instances of any fragment on that backend. This is simplistic, > because multiple fragments with same number of instance count, say 4 > non-blocking fragments each with 12 instances, only request the max instance > (12) admission slots rather than sum of it (48). > When COMPUTE_PROCESSING_COST is enabled, Planner will generate a CpuAsk > number that represent the cpu requirement of that query over a particular > executor group set. This number is an estimation of what is the largest > number of query fragments that can run in-parallel given the blocking > operator analysis. Therefore, the fragment trace that sums into that CpuAsk > number can be translated into 'slots_to_use' as well, which will be a closer > resemblance of maximum parallel execution of fragment instances. -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org