[kudu-CR] [ARM] Concurrent binary tree memory barriers fixed.

["Alexey Serbin (Code Review)" <ge...@cloudera.org>]

Alexey Serbin has posted comments on this change. ( http://gerrit.cloudera.org:8080/21127 )

Change subject: [ARM] Concurrent binary tree memory barriers fixed.
......................................................................


Patch Set 6:

(6 comments)

http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG@33
PS6, Line 33: The following 6 barriers need to be more strict:
Did you run the TestCBTree.TestScanPerformance scenario from the cbtree-test before and after this patch on x86_64?  What were the results?


http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG@45
PS6, Line 45: this
nit: these


http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG@46
PS6, Line 46: would resolve the issue
Have you actually tried that or this is just a hypothesis?


http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG@47
PS6, Line 47: c++
nit: C++


http://gerrit.cloudera.org:8080/#/c/21127/6//COMMIT_MSG@72
PS6, Line 72: By removing the packed PACKED we change nothing in the memory layout
How so?  What's the size of LeafNode and InternalNode after removing the packed attribute?


http://gerrit.cloudera.org:8080/#/c/21127/6/src/kudu/tablet/concurrent_btree.h
File src/kudu/tablet/concurrent_btree.h:

http://gerrit.cloudera.org:8080/#/c/21127/6/src/kudu/tablet/concurrent_btree.h@390
PS6, Line 390:   AtomicVersionValue VersionAcqRel() {
             :     return version_.load(std::memory_order_acq_rel);
             :   }
I'm curios how this make sense if by the specification the behavior of std::atomic<T>::load(std::memory_order_acq_rel) is undefined?  Am I missing something?

https://en.cppreference.com/w/cpp/atomic/atomic/load



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Ie7c02dc3b9444599ef680fa9b29ae7a4d39dd382
Gerrit-Change-Number: 21127
Gerrit-PatchSet: 6
Gerrit-Owner: Zoltan Martonka <zm...@cloudera.com>
Gerrit-Reviewer: Alexey Serbin <al...@apache.org>
Gerrit-Reviewer: Anonymous Coward (763)
Gerrit-Reviewer: Ashwani Raina <ar...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Zoltan Chovan <zc...@cloudera.com>
Gerrit-Reviewer: Zoltan Martonka <zm...@cloudera.com>
Gerrit-Comment-Date: Mon, 08 Apr 2024 19:06:55 +0000
Gerrit-HasComments: Yes