Youwei Wang has posted comments on this change. Change subject: IMPALA-2809: Improve ByteSwap with builtin function or SSE or AVX2. ......................................................................
Patch Set 11: (3 comments) http://gerrit.cloudera.org:8080/#/c/3081/11/be/src/benchmarks/bswap-benchmark.cc File be/src/benchmarks/bswap-benchmark.cc: Line 49: // SIMD 57.73 2.18X > I am surprised by this. Is a single branch making this code 20x-40x slower? Hi Jim. I suspect the following code: if (CpuInfo::IsSupported(CpuInfo::AVX2)) { I guess since there is a function in the conditional branch, it may be the reason why such much performance is consumed here. I will step in deeper to investigate this. Line 222: MACRO_TEST_FBS_CASE(8, 5) > remove the switch; instead: Done Line 260: /// FIXED_LEN_SIZE = 4: Decimal4Value, size of array element is 8x4 = 32bit > You've explain what FIXED_LEN_SIZE is, but I still don't know why we would Hi Jim. Previous codebase is written by Zuo Wang. I believe his idea is to illustrate the performance difference for different FIXED_LEN_SIZE here so to produce comprehensive and persuasive results. As for me, my idea is pretty simple and straightforward as you may have seen in the bit-util.inline.h file: I always try to apply the swap approach which can deal with the most bits when possible, not this enumerating-style approach. I am not sure which one is preferable for a benchmark case. -- To view, visit http://gerrit.cloudera.org:8080/3081 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I392ed5a8d5683f30f161282c228c1aedd7b648c1 Gerrit-PatchSet: 11 Gerrit-Project: Impala Gerrit-Branch: cdh5-trunk Gerrit-Owner: Youwei Wang <[email protected]> Gerrit-Reviewer: Alex Behm <[email protected]> Gerrit-Reviewer: Jim Apple <[email protected]> Gerrit-Reviewer: Marcel Kornacker <[email protected]> Gerrit-Reviewer: Mostafa Mokhtar <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Reviewer: Youwei Wang <[email protected]> Gerrit-HasComments: Yes
