Will Berkeley has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/11885 )

Change subject: Limit number of rowsets in compaction selection to 32 in TSAN 
mode
......................................................................


Patch Set 2:

Todd mentioned offline that it might be a good idea to limit the number of 
rowsets in a compaction even in release mode, since there is a memory cost per 
column per rowset involved in a compaction, up to 256KB.

At our column limit of 300 and the max number of rowsets in a compaction with 
default settings, 128, this means at worst using

300 * 128 * 256KB = 9.8GB

which is a lot. With a more-typical 50 columns, it's still over a GB of memory. 
I'm not sure what typical usage per column would be, though. Is it a lot less 
than 256KB?


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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I01ad4ba3a13995c194c3308d72c1eb9b611ef766
Gerrit-Change-Number: 11885
Gerrit-PatchSet: 2
Gerrit-Owner: Will Berkeley <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Will Berkeley <[email protected]>
Gerrit-Comment-Date: Tue, 06 Nov 2018 16:11:49 +0000
Gerrit-HasComments: No

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