linux-kernel - Re: 2.6.21-rc3-mm1 RSDL results

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Message-Id: <200703100819.18354.kernel@kolivas.org>
Date:	Sat, 10 Mar 2007 08:19:18 +1100
From:	Con Kolivas <kernel@...ivas.org>
To:	Matt Mackall <mpm@...enic.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	akpm@...ux-foundation.org
Subject: Re: 2.6.21-rc3-mm1 RSDL results

On Saturday 10 March 2007 08:07, Con Kolivas wrote:
> On Saturday 10 March 2007 07:46, Matt Mackall wrote:
> > My suspicion is the problem lies in giving too much quanta to
> > newly-started processes.
>
> Ah that's some nice detective work there. Mainline does some rather complex
> accounting on sched_fork including (possibly) a whole timer tick which rsdl
> does not do. make forks off continuously so what you say may well be
> correct. I'll see if I can try to revert to the mainline behaviour in
> sched_fork (which was obviously there for a reason).

Wow! Thanks Matt. You've found a real bug too. This seems to fix the qemu
 misbehaviour and bitmap errors so far too! Now can you please try this to see
 if it fixes your problem?

---
 kernel/sched.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Index: linux-2.6.21-rc3-mm1/kernel/sched.c
===================================================================
--- linux-2.6.21-rc3-mm1.orig/kernel/sched.c	2007-03-10 08:08:11.000000000 +1100
+++ linux-2.6.21-rc3-mm1/kernel/sched.c	2007-03-10 08:13:57.000000000 +1100
@@ -1560,7 +1560,7 @@ int fastcall wake_up_state(struct task_s
 	return try_to_wake_up(p, state, 0);
 }
 
-static void task_expired_entitlement(struct rq *rq, struct task_struct *p);
+static void task_running_tick(struct rq *rq, struct task_struct *p);
 /*
  * Perform scheduler related setup for a newly forked process p.
  * p is forked by current.
@@ -1621,10 +1621,8 @@ void fastcall sched_fork(struct task_str
 		 * left from its timeslice. Taking the runqueue lock is not
 		 * a problem.
 		 */
-		struct rq *rq = __task_rq_lock(current);
-
-		task_expired_entitlement(rq, current);
-		__task_rq_unlock(rq);
+		current->time_slice = 1;
+		task_running_tick(cpu_rq(cpu), current);
 	}
 	local_irq_enable();
 out:

-- 
-ck
-
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