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authorSimon Marlow <marlowsd@gmail.com>2016-08-30 20:55:10 +0100
committerSimon Marlow <marlowsd@gmail.com>2016-09-12 08:33:24 +0100
commit454033b54e2f7eef2354cc9d7ae7e7cba4dff09a (patch)
tree3577ed7b0b42e2acff1502673e1ee474fba31319 /rts/Threads.h
parent0e7ccf6d233c66b23a60de4e35e039f78ea3e162 (diff)
downloadhaskell-454033b54e2f7eef2354cc9d7ae7e7cba4dff09a.tar.gz
Add hs_try_putmvar()
Summary: This is a fast, non-blocking, asynchronous, interface to tryPutMVar that can be called from C/C++. It's useful for callback-based C/C++ APIs: the idea is that the callback invokes hs_try_putmvar(), and the Haskell code waits for the callback to run by blocking in takeMVar. The callback doesn't block - this is often a requirement of callback-based APIs. The callback wakes up the Haskell thread with minimal overhead and no unnecessary context-switches. There are a couple of benchmarks in testsuite/tests/concurrent/should_run. Some example results comparing hs_try_putmvar() with using a standard foreign export: ./hs_try_putmvar003 1 64 16 100 +RTS -s -N4 0.49s ./hs_try_putmvar003 2 64 16 100 +RTS -s -N4 2.30s hs_try_putmvar() is 4x faster for this workload (see the source for hs_try_putmvar003.hs for details of the workload). An alternative solution is to use the IO Manager for this. We've tried it, but there are problems with that approach: * Need to create a new file descriptor for each callback * The IO Manger thread(s) become a bottleneck * More potential for things to go wrong, e.g. throwing an exception in an IO Manager callback kills the IO Manager thread. Test Plan: validate; new unit tests Reviewers: niteria, erikd, ezyang, bgamari, austin, hvr Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2501
Diffstat (limited to 'rts/Threads.h')
-rw-r--r--rts/Threads.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/rts/Threads.h b/rts/Threads.h
index 01c493e53d..4588008e28 100644
--- a/rts/Threads.h
+++ b/rts/Threads.h
@@ -41,6 +41,8 @@ StgBool isThreadBound (StgTSO* tso);
void threadStackOverflow (Capability *cap, StgTSO *tso);
W_ threadStackUnderflow (Capability *cap, StgTSO *tso);
+rtsBool performTryPutMVar(Capability *cap, StgMVar *mvar, StgClosure *value);
+
#ifdef DEBUG
void printThreadBlockage (StgTSO *tso);
void printThreadStatus (StgTSO *t);