From: Simon Marlow <marlowsd@gmail.com>
Date: Wed, 13 Oct 2010 18:43:00 +0000 (+0000)
Subject: comment
X-Git-Tag: 2010-11-18~69
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=676b26bb57906b7fccf813771909ee19366e81e2

comment
---

diff --git a/rts/Threads.c b/rts/Threads.c
index 7344134..0dee734 100644
--- a/rts/Threads.c
+++ b/rts/Threads.c
@@ -284,6 +284,19 @@ unblock:
     // we'll block again.
     tso->why_blocked = NotBlocked;
     appendToRunQueue(cap,tso);
+
+    // We used to set the context switch flag here, which would
+    // trigger a context switch a short time in the future (at the end
+    // of the current nursery block).  The idea is that we have just
+    // woken up a thread, so we may need to load-balance and migrate
+    // threads to other CPUs.  On the other hand, setting the context
+    // switch flag here unfairly penalises the current thread by
+    // yielding its time slice too early.
+    //
+    // The synthetic benchmark nofib/smp/chan can be used to show the
+    // difference quite clearly.
+
+    // cap->context_switch = 1;
 }
 
 /* ----------------------------------------------------------------------------