bcm1480 doubled process accounting times

bcm1480 doubled process accounting times

[James E Wilson]

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Running a UP kernel on a bcm1480 board, I get nonsensical timing
results, like this:
release@unknown:~/tmp$ time ./a.out
real    0m22.906s
user    0m45.792s
sys     0m0.010s
According to my watch, this program took 23 seconds to run, so the real
time clock is OK.  It is process accounting that is broken.

I tracked this down to a problem with the function
bcm1480_timer_interrupt in the file sibyte/bcm1480/time.c.  This
function calls ll_timer_interrupt for cpu0, and ll_local_timer_interrupt
for all cpus.  However, both of these functions do process accounting. 
Thus processes running on cpu0 end up with doubled times.  This is very
obvious in a UP kernel where all processes run on cpu0.

The correct way to do this is to only call ll_local_timer interrupt if
this is not cpu0.  This can be seen in the mips-board/generic/time.c
file, and also in the sibyte/sb1250/time.c file, both of which handle
this correctly.  I fixed the bcm1480/time.c file by copying over the
correct code from the sb1250/time.c file.

With this fix, I now get sensible results.
release@unknown:~/tmp$ time ./a.out
real    0m22.903s
user    0m22.894s
sys     0m0.006s
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

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diff --git a/arch/mips/sibyte/bcm1480/setup.c b/arch/mips/sibyte/bcm1480/setup.c
diff --git a/arch/mips/sibyte/bcm1480/time.c b/arch/mips/sibyte/bcm1480/time.c
index e545752..efaf83e 100644
--- a/arch/mips/sibyte/bcm1480/time.c
+++ b/arch/mips/sibyte/bcm1480/time.c
@@ -110,17 +110,18 @@ void bcm1480_timer_interrupt(struct pt_r
 	__raw_writeq(M_SCD_TIMER_ENABLE|M_SCD_TIMER_MODE_CONTINUOUS,
 	      IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG)));
 
-	/*
-	 * CPU 0 handles the global timer interrupt job
-	 */
 	if (cpu == 0) {
+		/*
+		 * CPU 0 handles the global timer interrupt job
+		 */
 		ll_timer_interrupt(irq, regs);
 	}
-
-	/*
-	 * every CPU should do profiling and process accouting
-	 */
-	ll_local_timer_interrupt(irq, regs);
+	else {
+		/*
+		 * other CPUs should just do profiling and process accounting
+		 */
+		ll_local_timer_interrupt(irq, regs);
+	}
 }
 
 /*

Re: bcm1480 doubled process accounting times

[James E Wilson]

On Mon, 2006-02-27 at 15:04, James E Wilson wrote:
> Running a UP kernel on a bcm1480 board, I get nonsensical timing
> results

I'd like some info about how to get patches into the linux kernel.

I sent this patch in February.
  http://www.linux-mips.org/archives/linux-mips/2006-02/msg00404.html
I've been using it since then without apparent problem.  I didn't get
any comments from my earlier message, and I see the patch hasn't made it
into the tree on linux-mips yet.

How can I get this patch into the linux kernel tree?
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

Re: bcm1480 doubled process accounting times

[Ralf Baechle]

On Mon, Jun 12, 2006 at 01:40:25PM -0700, James E Wilson wrote:

> I'd like some info about how to get patches into the linux kernel.
> 
> I sent this patch in February.
>   http://www.linux-mips.org/archives/linux-mips/2006-02/msg00404.html
> I've been using it since then without apparent problem.  I didn't get
> any comments from my earlier message, and I see the patch hasn't made it
> into the tree on linux-mips yet.
> 
> How can I get this patch into the linux kernel tree?

Blame me, things do get lost.  Resending and yelling is the protocol.

Will apply in a minute.

  Ralf