Fix hang in tc microbenchmark + fix overlapping prep timers (supersede #127 + #129) #137
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Added a shared WaitGroup between vertex doAll and the nested, per vertex, edge doAll. Original code would hang because of the separate wait groups: after enqueueing a doAll in edge_tc_couting, harts wait for it to complete (tc_algos.cpp:42). However, this occurs on every hart because of the outer doAll in tc_no_chunk, therefore every hart is waiting and none is available to complete the work being waited on. When using one combined wait group, the outer doAll tasks are able to complete after enqueuing, but before completion of, the inner doAll tasks. Thus, harts are freed to complete the inner doAll and therefore forward progress.
This was referenced Jul 30, 2024
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tewaro
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Jul 31, 2024
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Add a comment about drvx, for when we refactor. |
tewaro
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Aug 5, 2024
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@AdityaAtulTewari added synchronization via |
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Fix a hang in the TC microbenchmark (originally #127):
Added a shared WaitGroup between vertex doAll and the nested, per vertex,
edge doAll. Original code would hang because of the separate wait groups:
after enqueueing a doAll in edge_tc_couting, harts wait for it to complete
(tc_algos.cpp:42). However, this occurs on every hart because of the outer
doAll in tc_no_chunk, therefore every hart is waiting and none is available
to complete the work being waited on. When using one combined wait group,
the outer doAll tasks are able to complete after enqueuing, but before
completion of, the inner doAll tasks. Thus, harts are freed to complete the
inner doAll and therefore forward progress.
Fix overlapping prep timers (originally #129):
Add a barrier to sequence the output of each node.