[PATCH] D28789: [lit] Support sharding testsuites, for parallel execution.

Graydon Hoare via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Jan 17 13:48:11 PST 2017

graydon added inline comments.

Comment at: utils/lit/lit/main.py:436
+                            shard_begin+1, shard_end))
+            run.tests = run.tests[shard_begin:shard_end]
ddunbar wrote:
> Would it be better to shard in a round robin fashion? There is some tendency for tests to be clumped by where they are defined, and where they are defined to be (weakly) correlated with how long they take to run, so that would distribute long running tests across machines, which should help reduce the deviation between total testing time among shards.
Considered it, but decided against based on the (possibly wrong) guess that the discovery-clumping order would have better locality in terms of what test-prerequisites are built, tested, and hot-in-cache. If you think round-robin will work better overall, I'm happy to change it.


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