Todd Lipcon has posted comments on this change. Change subject: [rpc] faster generation of KRPC call ID ......................................................................
Patch Set 2: Code-Review-1 (1 comment) don't think this is a worthwhile optimization since this isn't a hot code path http://gerrit.cloudera.org:8080/#/c/7813/2//COMMIT_MSG Commit Message: PS2, Line 48: const int u_bound = 800000000 + (random() % 100); : int n = 0; : for (int i = 0; i < u_bound; ++i) { : n = next_id(); : } I think your microbenchmark is invalid. With -O3 it compiles to this assembly: int main() { 4007a0: 48 83 ec 08 sub $0x8,%rsp srandom(time(nullptr)); 4007a4: 31 ff xor %edi,%edi 4007a6: e8 d5 ff ff ff callq 400780 <time@plt> 4007ab: 89 c7 mov %eax,%edi 4007ad: e8 8e ff ff ff callq 400740 <srandom@plt> const int u_bound = 800000000 + (random() % 100); 4007b2: e8 a9 ff ff ff callq 400760 <random@plt> 4007b7: 48 ba 0b d7 a3 70 3d movabs $0xa3d70a3d70a3d70b,%rdx 4007be: 0a d7 a3 4007c1: 48 89 c1 mov %rax,%rcx 4007c4: 48 f7 ea imul %rdx 4007c7: 48 89 c8 mov %rcx,%rax 4007ca: 48 c1 f8 3f sar $0x3f,%rax 4007ce: 48 01 ca add %rcx,%rdx 4007d1: 48 c1 fa 06 sar $0x6,%rdx 4007d5: 48 29 c2 sub %rax,%rdx 4007d8: 48 8d 04 92 lea (%rdx,%rdx,4),%rax ie it's turning the loop into a single constant time multiplication. -- To view, visit http://gerrit.cloudera.org:8080/7813 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I03726343d222bcd241c2c2a5a1670a672f8e5cb6 Gerrit-PatchSet: 2 Gerrit-Project: kudu Gerrit-Branch: master Gerrit-Owner: Alexey Serbin <aser...@cloudera.com> Gerrit-Reviewer: Adar Dembo <a...@cloudera.com> Gerrit-Reviewer: Kudu Jenkins Gerrit-Reviewer: Todd Lipcon <t...@apache.org> Gerrit-HasComments: Yes
