* [PATCH] drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function
@ 2017-05-05 8:05 Karim Eshapa
2017-06-25 2:49 ` Scott Wood
0 siblings, 1 reply; 2+ messages in thread
From: Karim Eshapa @ 2017-05-05 8:05 UTC (permalink / raw)
To: oss
Cc: claudiu.manoil, roy.pledge, colin.king, linuxppc-dev,
linux-arm-kernel, linux-kernel, Karim Eshapa
Change the comment for an entry check inside function
drain_mr_fqrni() with sleep for sufficient period
of time instead of long time proccessor cycles.
Signed-off-by: Karim Eshapa <karim.eshapa@gmail.com>
---
drivers/soc/fsl/qbman/qman.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c
index 18d391e..636a7d7 100644
--- a/drivers/soc/fsl/qbman/qman.c
+++ b/drivers/soc/fsl/qbman/qman.c
@@ -1071,18 +1071,19 @@ static int drain_mr_fqrni(struct qm_portal *p)
msg = qm_mr_current(p);
if (!msg) {
/*
- * if MR was full and h/w had other FQRNI entries to produce, we
- * need to allow it time to produce those entries once the
- * existing entries are consumed. A worst-case situation
- * (fully-loaded system) means h/w sequencers may have to do 3-4
- * other things before servicing the portal's MR pump, each of
- * which (if slow) may take ~50 qman cycles (which is ~200
- * processor cycles). So rounding up and then multiplying this
- * worst-case estimate by a factor of 10, just to be
- * ultra-paranoid, goes as high as 10,000 cycles. NB, we consume
- * one entry at a time, so h/w has an opportunity to produce new
- * entries well before the ring has been fully consumed, so
- * we're being *really* paranoid here.
+ * if MR was full and h/w had other FQRNI entries to
+ * produce, we need to allow it time to produce those
+ * entries once the existing entries are consumed.
+ * A worst-case situation (fully-loaded system) means
+ * h/w sequencers may have to do 3-4 other things
+ * before servicing the portal's MR pump, each of
+ * which (if slow) may take ~50 qman cycles
+ * (which is ~200 processor cycles). So sleep with
+ * 1 ms would be very efficient, after this period
+ * we can check if there is something produced.
+ * NB, we consume one entry at a time, so h/w has
+ * an opportunity to produce new entries well before
+ * the ring has been fully consumed.
*/
msleep(1);
msg = qm_mr_current(p);
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function
2017-05-05 8:05 [PATCH] drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function Karim Eshapa
@ 2017-06-25 2:49 ` Scott Wood
0 siblings, 0 replies; 2+ messages in thread
From: Scott Wood @ 2017-06-25 2:49 UTC (permalink / raw)
To: Karim Eshapa
Cc: roy.pledge, linux-kernel, claudiu.manoil, colin.king,
linuxppc-dev, linux-arm-kernel
On Fri, May 05, 2017 at 10:05:56AM +0200, Karim Eshapa wrote:
> Change the comment for an entry check inside function
> drain_mr_fqrni() with sleep for sufficient period
> of time instead of long time proccessor cycles.
>
> Signed-off-by: Karim Eshapa <karim.eshapa@gmail.com>
> ---
> drivers/soc/fsl/qbman/qman.c | 25 +++++++++++++------------
> 1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c
> index 18d391e..636a7d7 100644
> --- a/drivers/soc/fsl/qbman/qman.c
> +++ b/drivers/soc/fsl/qbman/qman.c
> @@ -1071,18 +1071,19 @@ static int drain_mr_fqrni(struct qm_portal *p)
> msg = qm_mr_current(p);
> if (!msg) {
> /*
> - * if MR was full and h/w had other FQRNI entries to produce, we
> - * need to allow it time to produce those entries once the
> - * existing entries are consumed. A worst-case situation
> - * (fully-loaded system) means h/w sequencers may have to do 3-4
> - * other things before servicing the portal's MR pump, each of
> - * which (if slow) may take ~50 qman cycles (which is ~200
> - * processor cycles). So rounding up and then multiplying this
> - * worst-case estimate by a factor of 10, just to be
> - * ultra-paranoid, goes as high as 10,000 cycles. NB, we consume
> - * one entry at a time, so h/w has an opportunity to produce new
> - * entries well before the ring has been fully consumed, so
> - * we're being *really* paranoid here.
> + * if MR was full and h/w had other FQRNI entries to
> + * produce, we need to allow it time to produce those
> + * entries once the existing entries are consumed.
> + * A worst-case situation (fully-loaded system) means
> + * h/w sequencers may have to do 3-4 other things
> + * before servicing the portal's MR pump, each of
> + * which (if slow) may take ~50 qman cycles
> + * (which is ~200 processor cycles). So sleep with
> + * 1 ms would be very efficient, after this period
> + * we can check if there is something produced.
> + * NB, we consume one entry at a time, so h/w has
> + * an opportunity to produce new entries well before
> + * the ring has been fully consumed.
Do you mean "sufficient" here rather than "efficient"? It's far less
inefficient than what the code was previously doing, but still...
Otherwise, looks good.
-Scott
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2017-05-05 8:05 [PATCH] drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function Karim Eshapa
2017-06-25 2:49 ` Scott Wood
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