Tim Armstrong has submitted this change and it was merged. Change subject: IMPALA-3168: replace HashTable parameters with constants ......................................................................
IMPALA-3168: replace HashTable parameters with constants This addresses the regression for small-ndv aggs resulting from prefetching. The idea is that for small-ndv aggs prefetching increases the # of instructions and memory references, but doesn't provide any compensating benefit. This change replaces constant values in the hash-table code, which reduces the instruction count and # of memory references in aggregations. Preliminary perf results show that a low-NDV decimal agg is around 20% faster (2.1s -> 1.7s) and a high-NDV decimal agg is around 7% faster (15s -> 14s). I haven't investigated how much of the speedup is reduced codegen time. Change-Id: I483a19662c90ca54bc21d60fd6ba97dbed93eaef Reviewed-on: http://gerrit.cloudera.org:8080/3088 Tested-by: Internal Jenkins Reviewed-by: Dan Hecht <[email protected]> --- M be/src/codegen/llvm-codegen.cc M be/src/codegen/llvm-codegen.h M be/src/exec/hash-table-test.cc M be/src/exec/hash-table.cc M be/src/exec/hash-table.h M be/src/exec/hash-table.inline.h M be/src/exec/partitioned-aggregation-node.cc M be/src/exec/partitioned-hash-join-node.cc 8 files changed, 215 insertions(+), 56 deletions(-) Approvals: Internal Jenkins: Verified Dan Hecht: Looks good to me, approved -- To view, visit http://gerrit.cloudera.org:8080/3088 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: merged Gerrit-Change-Id: I483a19662c90ca54bc21d60fd6ba97dbed93eaef Gerrit-PatchSet: 8 Gerrit-Project: Impala Gerrit-Branch: cdh5-trunk Gerrit-Owner: Tim Armstrong <[email protected]> Gerrit-Reviewer: Dan Hecht <[email protected]> Gerrit-Reviewer: Internal Jenkins Gerrit-Reviewer: Michael Ho Gerrit-Reviewer: Michael Ho <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]>
