Re: [cpuops cmpxchg V2 4/5] vmstat: User per cpu atomics to avoidinterrupt disable / enable

[Christoph Lameter]

On Wed, 15 Dec 2010, Tejun Heo wrote:

> +		/*
> +		 * The fetching of the stat_threshold is racy. We may apply
> +		 * a counter threshold to the wrong the cpu if we get
> +		 * rescheduled while executing here. However, the following
> +		 * will apply the threshold again and therefore bring the
> +		 * counter under the threshold.
> +		 */
>
> What does "the following" mean here?  Later executions of the
> function?  It seems like the counter can go out of the threshold at
> least temporarily, which probably is okay but I think the comment can
> be improved a bit.

I meant later execution of the function. I will fix the comment.

Subject: vmstat comment fix

Clarify comments for the threshold a bit.

Signed-off-by: Christoh Lameter <cl@xxxxxxxxx>

---
 mm/vmstat.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c	2010-12-15 10:57:44.000000000 -0600
+++ linux-2.6/mm/vmstat.c	2010-12-15 10:58:46.000000000 -0600
@@ -277,9 +277,12 @@ static inline void mod_state(struct zone
 		/*
 		 * The fetching of the stat_threshold is racy. We may apply
 		 * a counter threshold to the wrong the cpu if we get
-		 * rescheduled while executing here. However, the following
-		 * will apply the threshold again and therefore bring the
-		 * counter under the threshold.
+		 * rescheduled while executing here. However, the next
+		 * counter update will apply the threshold again and
+		 * therefore bring the counter under the threshold again.
+		 *
+		 * Most of the time the thresholds are the same anyways
+		 * for all cpus in a zone.
 		 */
 		t = this_cpu_read(pcp->stat_threshold);

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/