drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function

Submitted by Karim Eshapa on May 5, 2017, 8:05 a.m.

Details

Message ID 1493971556-14918-1-git-send-email-karim.eshapa@gmail.com
State New
Headers show

Commit Message

Karim Eshapa May 5, 2017, 8:05 a.m.
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(-)

Comments

Scott Wood June 25, 2017, 2:49 a.m.
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
Karim Eshapa June 25, 2017, 3:02 p.m.
>Do you mean "sufficient" here rather than "efficient"?  It's far less
>inefficient than what the code was previously doing, but still...

Yes, I'm gonna send a new fix for the comment patch and
change the subject of the previous patch soc/qman

Thanks,
Karim


On 25 June 2017 at 04:49, Scott Wood <oss@buserror.net> wrote:

> 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
>

Patch hide | download patch | download mbox

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);