* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
@ 2020-08-17 22:56 ` Tao Ren
0 siblings, 0 replies; 16+ messages in thread
From: Tao Ren @ 2020-08-17 22:56 UTC (permalink / raw)
To: Felipe Balbi
Cc: linux-aspeed, taoren, Andrew Jeffery, Greg Kroah-Hartman,
openbmc, linux-usb, linux-kernel, Stephen Boyd, Joel Stanley,
Benjamin Herrenschmidt, Chunfeng Yun, linux-arm-kernel
On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
>
> Hi,
>
> rentao.bupt@gmail.com writes:
> > From: Tao Ren <rentao.bupt@gmail.com>
> >
> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
> > improve vhub port irq handling"): for_each_set_bit() is replaced with
> > simple for() loop because for() loop runs faster on ASPEED BMC.
> >
> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> > ---
> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
> > 2 files changed, 6 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> > index cdf96911e4b1..be7bb64e3594 100644
> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
> >
> > /* Handle device interrupts */
> > if (istat & vhub->port_irq_mask) {
> > - unsigned long bitmap = istat;
> > - int offset = VHUB_IRQ_DEV1_BIT;
> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
> > -
> > - for_each_set_bit_from(offset, &bitmap, size) {
> > - i = offset - VHUB_IRQ_DEV1_BIT;
> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
> > + for (i = 0; i < vhub->max_ports; i++) {
> > + if (istat & VHUB_DEV_IRQ(i))
> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>
> how have you measured your statement above? for_each_set_bit() does
> exactly what you did. Unless your architecture has an instruction which
> helps finds the next set bit (like cls on ARM), which, then, makes it
> much faster.
I did some testing and result shows for() loop runs faster than
for_each_set_bit() loop. Please refer to details below (discussion with
Benjamin in the original patch) and kindly let me know your suggestions.
> On Mon, 2020-04-06 at 23:02 -0700, Tao Ren wrote:
> > I ran some testing on my ast2400 and ast2500 BMC and looks like the
> > for() loop runs faster than for_each_set_bit_from() loop in my
> > environment. I'm not sure if something needs to be revised in my test
> > code, but please kindly share your suggestions:
> >
> > I use get_cycles() to calculate execution time of 2 different loops, and
> > ast_vhub_dev_irq() is replaced with barrier() to avoid "noise"; below
> > are the results:
> >
> > - when downstream port number is 5 and only 1 irq bit is set, it takes
> > ~30 cycles to finish for_each_set_bit() loop, and 20-25 cycles to
> > finish the for() loop.
> >
> > - if downstream port number is 5 and all 5 bits are set, then
> > for_each_set_bit() loop takes ~50 cycles and for() loop takes ~25
> > cycles.
> >
> > - when I increase downsteam port number to 16 and set 1 irq bit, the
> > for_each_set_bit() loop takes ~30 cycles and for() loop takes 25
> > cycles. It's a little surprise to me because I thought for() loop
> > would cost 60+ cycles (3 times of the value when port number is 5).
> >
> > - if downstream port number is 16 and all irq status bits are set,
> > then for_each_set_bit() loop takes 60-70 cycles and for() loop takes
> > 30+ cycles.
Cheers,
Tao
_______________________________________________
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linux-arm-kernel@lists.infradead.org
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^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
2020-08-17 22:56 ` Tao Ren
@ 2020-08-31 9:54 ` Felipe Balbi
-1 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:54 UTC (permalink / raw)
To: Tao Ren
Cc: Greg Kroah-Hartman, Joel Stanley, Andrew Jeffery,
Benjamin Herrenschmidt, Chunfeng Yun, Stephen Boyd, linux-usb,
linux-arm-kernel, linux-aspeed, linux-kernel, openbmc, taoren
[-- Attachment #1: Type: text/plain, Size: 2175 bytes --]
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
> On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
>>
>> Hi,
>>
>> rentao.bupt@gmail.com writes:
>> > From: Tao Ren <rentao.bupt@gmail.com>
>> >
>> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
>> > improve vhub port irq handling"): for_each_set_bit() is replaced with
>> > simple for() loop because for() loop runs faster on ASPEED BMC.
>> >
>> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
>> > ---
>> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
>> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
>> > 2 files changed, 6 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your suggestions.
no strong feelings, just surprised that you're already worried about
20~40 cycles of cpu time ;-)
Patch applied for next merge window
--
balbi
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^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
@ 2020-08-31 9:54 ` Felipe Balbi
0 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:54 UTC (permalink / raw)
To: Tao Ren
Cc: linux-aspeed, taoren, Andrew Jeffery, Greg Kroah-Hartman,
openbmc, linux-usb, linux-kernel, Stephen Boyd, Joel Stanley,
Benjamin Herrenschmidt, Chunfeng Yun, linux-arm-kernel
[-- Attachment #1.1: Type: text/plain, Size: 2175 bytes --]
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
> On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
>>
>> Hi,
>>
>> rentao.bupt@gmail.com writes:
>> > From: Tao Ren <rentao.bupt@gmail.com>
>> >
>> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
>> > improve vhub port irq handling"): for_each_set_bit() is replaced with
>> > simple for() loop because for() loop runs faster on ASPEED BMC.
>> >
>> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
>> > ---
>> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
>> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
>> > 2 files changed, 6 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your suggestions.
no strong feelings, just surprised that you're already worried about
20~40 cycles of cpu time ;-)
Patch applied for next merge window
--
balbi
[-- Attachment #1.2: signature.asc --]
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[-- Attachment #2: Type: text/plain, Size: 176 bytes --]
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
2020-08-17 22:56 ` Tao Ren
@ 2020-08-31 9:54 ` Felipe Balbi
-1 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:54 UTC (permalink / raw)
To: Tao Ren
Cc: Greg Kroah-Hartman, Joel Stanley, Andrew Jeffery,
Benjamin Herrenschmidt, Chunfeng Yun, Stephen Boyd, linux-usb,
linux-arm-kernel, linux-aspeed, linux-kernel, openbmc, taoren
[-- Attachment #1: Type: text/plain, Size: 2175 bytes --]
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
> On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
>>
>> Hi,
>>
>> rentao.bupt@gmail.com writes:
>> > From: Tao Ren <rentao.bupt@gmail.com>
>> >
>> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
>> > improve vhub port irq handling"): for_each_set_bit() is replaced with
>> > simple for() loop because for() loop runs faster on ASPEED BMC.
>> >
>> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
>> > ---
>> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
>> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
>> > 2 files changed, 6 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your suggestions.
no strong feelings, just surprised that you're already worried about
20~40 cycles of cpu time ;-)
Patch applied for next merge window
--
balbi
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 857 bytes --]
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
@ 2020-08-31 9:54 ` Felipe Balbi
0 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:54 UTC (permalink / raw)
To: Tao Ren
Cc: linux-aspeed, taoren, Andrew Jeffery, Greg Kroah-Hartman,
openbmc, linux-usb, linux-kernel, Stephen Boyd, Joel Stanley,
Benjamin Herrenschmidt, Chunfeng Yun, linux-arm-kernel
[-- Attachment #1.1: Type: text/plain, Size: 2175 bytes --]
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
> On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
>>
>> Hi,
>>
>> rentao.bupt@gmail.com writes:
>> > From: Tao Ren <rentao.bupt@gmail.com>
>> >
>> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
>> > improve vhub port irq handling"): for_each_set_bit() is replaced with
>> > simple for() loop because for() loop runs faster on ASPEED BMC.
>> >
>> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
>> > ---
>> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
>> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
>> > 2 files changed, 6 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your suggestions.
no strong feelings, just surprised that you're already worried about
20~40 cycles of cpu time ;-)
Patch applied for next merge window
--
balbi
[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 857 bytes --]
[-- Attachment #2: Type: text/plain, Size: 176 bytes --]
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
2020-08-31 9:54 ` Felipe Balbi
@ 2020-08-31 23:26 ` Tao Ren
-1 siblings, 0 replies; 16+ messages in thread
From: Tao Ren @ 2020-08-31 23:26 UTC (permalink / raw)
To: Felipe Balbi
Cc: Greg Kroah-Hartman, Joel Stanley, Andrew Jeffery,
Benjamin Herrenschmidt, Chunfeng Yun, Stephen Boyd, linux-usb,
linux-arm-kernel, linux-aspeed, linux-kernel, openbmc, taoren
On Mon, Aug 31, 2020 at 12:54:57PM +0300, Felipe Balbi wrote:
>
> Hi,
>
> Tao Ren <rentao.bupt@gmail.com> writes:
> > On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
> >>
> >> Hi,
> >>
> >> rentao.bupt@gmail.com writes:
> >> > From: Tao Ren <rentao.bupt@gmail.com>
> >> >
> >> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
> >> > improve vhub port irq handling"): for_each_set_bit() is replaced with
> >> > simple for() loop because for() loop runs faster on ASPEED BMC.
> >> >
> >> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> >> > ---
> >> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
> >> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
> >> > 2 files changed, 6 insertions(+), 7 deletions(-)
> >> >
> >> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > index cdf96911e4b1..be7bb64e3594 100644
> >> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
> >> >
> >> > /* Handle device interrupts */
> >> > if (istat & vhub->port_irq_mask) {
> >> > - unsigned long bitmap = istat;
> >> > - int offset = VHUB_IRQ_DEV1_BIT;
> >> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
> >> > -
> >> > - for_each_set_bit_from(offset, &bitmap, size) {
> >> > - i = offset - VHUB_IRQ_DEV1_BIT;
> >> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
> >> > + for (i = 0; i < vhub->max_ports; i++) {
> >> > + if (istat & VHUB_DEV_IRQ(i))
> >> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
> >>
> >> how have you measured your statement above? for_each_set_bit() does
> >> exactly what you did. Unless your architecture has an instruction which
> >> helps finds the next set bit (like cls on ARM), which, then, makes it
> >> much faster.
> >
> > I did some testing and result shows for() loop runs faster than
> > for_each_set_bit() loop. Please refer to details below (discussion with
> > Benjamin in the original patch) and kindly let me know your suggestions.
>
> no strong feelings, just surprised that you're already worried about
> 20~40 cycles of cpu time ;-)
>
> Patch applied for next merge window
Thanks Felipe. Ben had some concerns about interrupt handling cost on
AST2400 BMC (ARM9), hence we did the comparison and noticed the small
difference :)
Cheers,
Tao
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
@ 2020-08-31 23:26 ` Tao Ren
0 siblings, 0 replies; 16+ messages in thread
From: Tao Ren @ 2020-08-31 23:26 UTC (permalink / raw)
To: Felipe Balbi
Cc: linux-aspeed, taoren, Andrew Jeffery, Greg Kroah-Hartman,
openbmc, linux-usb, linux-kernel, Stephen Boyd, Joel Stanley,
Benjamin Herrenschmidt, Chunfeng Yun, linux-arm-kernel
On Mon, Aug 31, 2020 at 12:54:57PM +0300, Felipe Balbi wrote:
>
> Hi,
>
> Tao Ren <rentao.bupt@gmail.com> writes:
> > On Mon, Aug 17, 2020 at 04:49:32PM +0300, Felipe Balbi wrote:
> >>
> >> Hi,
> >>
> >> rentao.bupt@gmail.com writes:
> >> > From: Tao Ren <rentao.bupt@gmail.com>
> >> >
> >> > This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
> >> > improve vhub port irq handling"): for_each_set_bit() is replaced with
> >> > simple for() loop because for() loop runs faster on ASPEED BMC.
> >> >
> >> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> >> > ---
> >> > drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
> >> > drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
> >> > 2 files changed, 6 insertions(+), 7 deletions(-)
> >> >
> >> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > index cdf96911e4b1..be7bb64e3594 100644
> >> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
> >> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
> >> >
> >> > /* Handle device interrupts */
> >> > if (istat & vhub->port_irq_mask) {
> >> > - unsigned long bitmap = istat;
> >> > - int offset = VHUB_IRQ_DEV1_BIT;
> >> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
> >> > -
> >> > - for_each_set_bit_from(offset, &bitmap, size) {
> >> > - i = offset - VHUB_IRQ_DEV1_BIT;
> >> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
> >> > + for (i = 0; i < vhub->max_ports; i++) {
> >> > + if (istat & VHUB_DEV_IRQ(i))
> >> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
> >>
> >> how have you measured your statement above? for_each_set_bit() does
> >> exactly what you did. Unless your architecture has an instruction which
> >> helps finds the next set bit (like cls on ARM), which, then, makes it
> >> much faster.
> >
> > I did some testing and result shows for() loop runs faster than
> > for_each_set_bit() loop. Please refer to details below (discussion with
> > Benjamin in the original patch) and kindly let me know your suggestions.
>
> no strong feelings, just surprised that you're already worried about
> 20~40 cycles of cpu time ;-)
>
> Patch applied for next merge window
Thanks Felipe. Ben had some concerns about interrupt handling cost on
AST2400 BMC (ARM9), hence we did the comparison and noticed the small
difference :)
Cheers,
Tao
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^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
2020-08-17 22:56 ` Tao Ren
@ 2020-08-31 9:56 ` Felipe Balbi
-1 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:56 UTC (permalink / raw)
To: Tao Ren
Cc: Greg Kroah-Hartman, Joel Stanley, Andrew Jeffery,
Benjamin Herrenschmidt, Chunfeng Yun, Stephen Boyd, linux-usb,
linux-arm-kernel, linux-aspeed, linux-kernel, openbmc, taoren
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your
> suggestions.
no strong feelings, just surprised you're already worried about 20~40
cycles of cpu time ;-)
patch queued for next merge window
--
balbi
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
@ 2020-08-31 9:56 ` Felipe Balbi
0 siblings, 0 replies; 16+ messages in thread
From: Felipe Balbi @ 2020-08-31 9:56 UTC (permalink / raw)
To: Tao Ren
Cc: linux-aspeed, taoren, Andrew Jeffery, Greg Kroah-Hartman,
openbmc, linux-usb, linux-kernel, Stephen Boyd, Joel Stanley,
Benjamin Herrenschmidt, Chunfeng Yun, linux-arm-kernel
Hi,
Tao Ren <rentao.bupt@gmail.com> writes:
>> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > index cdf96911e4b1..be7bb64e3594 100644
>> > --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c
>> > @@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data)
>> >
>> > /* Handle device interrupts */
>> > if (istat & vhub->port_irq_mask) {
>> > - unsigned long bitmap = istat;
>> > - int offset = VHUB_IRQ_DEV1_BIT;
>> > - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports;
>> > -
>> > - for_each_set_bit_from(offset, &bitmap, size) {
>> > - i = offset - VHUB_IRQ_DEV1_BIT;
>> > - ast_vhub_dev_irq(&vhub->ports[i].dev);
>> > + for (i = 0; i < vhub->max_ports; i++) {
>> > + if (istat & VHUB_DEV_IRQ(i))
>> > + ast_vhub_dev_irq(&vhub->ports[i].dev);
>>
>> how have you measured your statement above? for_each_set_bit() does
>> exactly what you did. Unless your architecture has an instruction which
>> helps finds the next set bit (like cls on ARM), which, then, makes it
>> much faster.
>
> I did some testing and result shows for() loop runs faster than
> for_each_set_bit() loop. Please refer to details below (discussion with
> Benjamin in the original patch) and kindly let me know your
> suggestions.
no strong feelings, just surprised you're already worried about 20~40
cycles of cpu time ;-)
patch queued for next merge window
--
balbi
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 16+ messages in thread