From 5d52d9b64c21dcf77849866584744722f8121389 Mon Sep 17 00:00:00 2001 From: Simon Marlow Date: Mon, 29 Mar 2010 14:44:56 +0000 Subject: New implementation of BLACKHOLEs This replaces the global blackhole_queue with a clever scheme that enables us to queue up blocked threads on the closure that they are blocked on, while still avoiding atomic instructions in the common case. Advantages: - gets rid of a locked global data structure and some tricky GC code (replacing it with some per-thread data structures and different tricky GC code :) - wakeups are more prompt: parallel/concurrent performance should benefit. I haven't seen anything dramatic in the parallel benchmarks so far, but a couple of threading benchmarks do improve a bit. - waking up a thread blocked on a blackhole is now O(1) (e.g. if it is the target of throwTo). - less sharing and better separation of Capabilities: communication is done with messages, the data structures are strictly owned by a Capability and cannot be modified except by sending messages. - this change will utlimately enable us to do more intelligent scheduling when threads block on each other. This is what started off the whole thing, but it isn't done yet (#3838). I'll be documenting all this on the wiki in due course. --- rts/Schedule.h | 9 --------- 1 file changed, 9 deletions(-) (limited to 'rts/Schedule.h') diff --git a/rts/Schedule.h b/rts/Schedule.h index 2412285d29..0db2b1ed84 100644 --- a/rts/Schedule.h +++ b/rts/Schedule.h @@ -86,15 +86,6 @@ extern StgTSO *blocked_queue_hd, *blocked_queue_tl; extern StgTSO *sleeping_queue; #endif -/* Set to rtsTrue if there are threads on the blackhole_queue, and - * it is possible that one or more of them may be available to run. - * This flag is set to rtsFalse after we've checked the queue, and - * set to rtsTrue just before we run some Haskell code. It is used - * to decide whether we should yield the Capability or not. - * Locks required : none (see scheduleCheckBlackHoles()). - */ -extern rtsBool blackholes_need_checking; - extern rtsBool heap_overflow; #if defined(THREADED_RTS) -- cgit v1.2.1