[PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[I Hsin Cheng]

Simplify the procedure of CPU random selection under
"clocksource_verify_choose_cpus()" with "cpumask_next_wrap()". The
logic is still the same but with this change it can shrink the code size
by 18 bytes and increase readability.

$ ./scripts/bloat-o-meter vmlinux_old vmlinux_new
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-18 (-18)
Function                                     old     new   delta
clocksource_verify_percpu                   1064    1046     -18

Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
---
 kernel/time/clocksource.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index bb48498ebb5a..ab580873408b 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -343,9 +343,7 @@ static void clocksource_verify_choose_cpus(void)
 	 */
 	for (i = 1; i < n; i++) {
 		cpu = get_random_u32_below(nr_cpu_ids);
-		cpu = cpumask_next(cpu - 1, cpu_online_mask);
-		if (cpu >= nr_cpu_ids)
-			cpu = cpumask_first(cpu_online_mask);
+		cpu = cpumask_next_wrap(cpu - 1, cpu_online_mask);
 		if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
 			cpumask_set_cpu(cpu, &cpus_chosen);
 	}
-- 
2.43.0

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[John Stultz]

On Wed, Jun 11, 2025 at 3:45 AM I Hsin Cheng <richard120310@gmail.com> wrote:
>
> Simplify the procedure of CPU random selection under
> "clocksource_verify_choose_cpus()" with "cpumask_next_wrap()". The
> logic is still the same but with this change it can shrink the code size
> by 18 bytes and increase readability.
>
> $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-18 (-18)
> Function                                     old     new   delta
> clocksource_verify_percpu                   1064    1046     -18
>
> Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
> ---
>  kernel/time/clocksource.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index bb48498ebb5a..ab580873408b 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -343,9 +343,7 @@ static void clocksource_verify_choose_cpus(void)
>          */
>         for (i = 1; i < n; i++) {
>                 cpu = get_random_u32_below(nr_cpu_ids);
> -               cpu = cpumask_next(cpu - 1, cpu_online_mask);
> -               if (cpu >= nr_cpu_ids)
> -                       cpu = cpumask_first(cpu_online_mask);
> +               cpu = cpumask_next_wrap(cpu - 1, cpu_online_mask);
>                 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
>                         cpumask_set_cpu(cpu, &cpus_chosen);
>         }

I think Yury submitted the same change here recently:
  https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/

Though, I think he has another iteration needed as Thomas had feedback
on the subject line.

The bloat-o-meter data is a nice inclusion here!

Yury: Would you be open to adapting I Hsin Cheng's commit message into
yours and adding them as co-author via the Co-developed-by: tag?
(Assuming I Hsin Cheng agrees - See
Documentation/process/submitting-patches.rst for how to do this
properly).

thanks
-john

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[Yury Norov]

On Wed, Jun 11, 2025 at 11:35:13AM -0700, John Stultz wrote:
> On Wed, Jun 11, 2025 at 3:45 AM I Hsin Cheng <richard120310@gmail.com> wrote:
> >
> > Simplify the procedure of CPU random selection under
> > "clocksource_verify_choose_cpus()" with "cpumask_next_wrap()". The
> > logic is still the same but with this change it can shrink the code size
> > by 18 bytes and increase readability.
> >
> > $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new
> > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-18 (-18)
> > Function                                     old     new   delta
> > clocksource_verify_percpu                   1064    1046     -18
> >
> > Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
> > ---
> >  kernel/time/clocksource.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> > index bb48498ebb5a..ab580873408b 100644
> > --- a/kernel/time/clocksource.c
> > +++ b/kernel/time/clocksource.c
> > @@ -343,9 +343,7 @@ static void clocksource_verify_choose_cpus(void)
> >          */
> >         for (i = 1; i < n; i++) {
> >                 cpu = get_random_u32_below(nr_cpu_ids);
> > -               cpu = cpumask_next(cpu - 1, cpu_online_mask);
> > -               if (cpu >= nr_cpu_ids)
> > -                       cpu = cpumask_first(cpu_online_mask);
> > +               cpu = cpumask_next_wrap(cpu - 1, cpu_online_mask);
> >                 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
> >                         cpumask_set_cpu(cpu, &cpus_chosen);
> >         }
> 
> I think Yury submitted the same change here recently:
>   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> 
> Though, I think he has another iteration needed as Thomas had feedback
> on the subject line.
> 
> The bloat-o-meter data is a nice inclusion here!
> 
> Yury: Would you be open to adapting I Hsin Cheng's commit message into
> yours and adding them as co-author via the Co-developed-by: tag?
> (Assuming I Hsin Cheng agrees - See
> Documentation/process/submitting-patches.rst for how to do this
> properly).

Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
I Hsin, do you agree?

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[I Hsin Cheng]

On Wed, Jun 11, 2025 at 03:04:42PM -0400, Yury Norov wrote:
> On Wed, Jun 11, 2025 at 11:35:13AM -0700, John Stultz wrote:
> > On Wed, Jun 11, 2025 at 3:45 AM I Hsin Cheng <richard120310@gmail.com> wrote:
> > >
> > > Simplify the procedure of CPU random selection under
> > > "clocksource_verify_choose_cpus()" with "cpumask_next_wrap()". The
> > > logic is still the same but with this change it can shrink the code size
> > > by 18 bytes and increase readability.
> > >
> > > $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new
> > > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-18 (-18)
> > > Function                                     old     new   delta
> > > clocksource_verify_percpu                   1064    1046     -18
> > >
> > > Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
> > > ---
> > >  kernel/time/clocksource.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> > > index bb48498ebb5a..ab580873408b 100644
> > > --- a/kernel/time/clocksource.c
> > > +++ b/kernel/time/clocksource.c
> > > @@ -343,9 +343,7 @@ static void clocksource_verify_choose_cpus(void)
> > >          */
> > >         for (i = 1; i < n; i++) {
> > >                 cpu = get_random_u32_below(nr_cpu_ids);
> > > -               cpu = cpumask_next(cpu - 1, cpu_online_mask);
> > > -               if (cpu >= nr_cpu_ids)
> > > -                       cpu = cpumask_first(cpu_online_mask);
> > > +               cpu = cpumask_next_wrap(cpu - 1, cpu_online_mask);
> > >                 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
> > >                         cpumask_set_cpu(cpu, &cpus_chosen);
> > >         }
> > 
> > I think Yury submitted the same change here recently:
> >   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> > 
> > Though, I think he has another iteration needed as Thomas had feedback
> > on the subject line.
> > 
> > The bloat-o-meter data is a nice inclusion here!
> > 
> > Yury: Would you be open to adapting I Hsin Cheng's commit message into
> > yours and adding them as co-author via the Co-developed-by: tag?
> > (Assuming I Hsin Cheng agrees - See
> > Documentation/process/submitting-patches.rst for how to do this
> > properly).
> 
> Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
> I Hsin, do you agree?

Sure thing, so do I need to apply the tag myself or we'll follow Yury's
patch work?

Best regards,
I Hsin Cheng

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[Yury Norov]

On Thu, Jun 12, 2025 at 03:45:36PM +0800, I Hsin Cheng wrote:
> On Wed, Jun 11, 2025 at 03:04:42PM -0400, Yury Norov wrote:
> > On Wed, Jun 11, 2025 at 11:35:13AM -0700, John Stultz wrote:
> > > On Wed, Jun 11, 2025 at 3:45 AM I Hsin Cheng <richard120310@gmail.com> wrote:
> > > >
> > > > Simplify the procedure of CPU random selection under
> > > > "clocksource_verify_choose_cpus()" with "cpumask_next_wrap()". The
> > > > logic is still the same but with this change it can shrink the code size
> > > > by 18 bytes and increase readability.
> > > >
> > > > $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new
> > > > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-18 (-18)
> > > > Function                                     old     new   delta
> > > > clocksource_verify_percpu                   1064    1046     -18
> > > >
> > > > Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
> > > > ---
> > > >  kernel/time/clocksource.c | 4 +---
> > > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > > >
> > > > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> > > > index bb48498ebb5a..ab580873408b 100644
> > > > --- a/kernel/time/clocksource.c
> > > > +++ b/kernel/time/clocksource.c
> > > > @@ -343,9 +343,7 @@ static void clocksource_verify_choose_cpus(void)
> > > >          */
> > > >         for (i = 1; i < n; i++) {
> > > >                 cpu = get_random_u32_below(nr_cpu_ids);
> > > > -               cpu = cpumask_next(cpu - 1, cpu_online_mask);
> > > > -               if (cpu >= nr_cpu_ids)
> > > > -                       cpu = cpumask_first(cpu_online_mask);
> > > > +               cpu = cpumask_next_wrap(cpu - 1, cpu_online_mask);
> > > >                 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
> > > >                         cpumask_set_cpu(cpu, &cpus_chosen);
> > > >         }
> > > 
> > > I think Yury submitted the same change here recently:
> > >   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> > > 
> > > Though, I think he has another iteration needed as Thomas had feedback
> > > on the subject line.
> > > 
> > > The bloat-o-meter data is a nice inclusion here!
> > > 
> > > Yury: Would you be open to adapting I Hsin Cheng's commit message into
> > > yours and adding them as co-author via the Co-developed-by: tag?
> > > (Assuming I Hsin Cheng agrees - See
> > > Documentation/process/submitting-patches.rst for how to do this
> > > properly).
> > 
> > Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
> > I Hsin, do you agree?
> 
> Sure thing, so do I need to apply the tag myself or we'll follow Yury's
> patch work?

I'll send v2 and include your results.

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[Yury Norov]

> > > > I think Yury submitted the same change here recently:
> > > >   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> > > > 
> > > > Though, I think he has another iteration needed as Thomas had feedback
> > > > on the subject line.
> > > > 
> > > > The bloat-o-meter data is a nice inclusion here!
> > > > 
> > > > Yury: Would you be open to adapting I Hsin Cheng's commit message into
> > > > yours and adding them as co-author via the Co-developed-by: tag?
> > > > (Assuming I Hsin Cheng agrees - See
> > > > Documentation/process/submitting-patches.rst for how to do this
> > > > properly).
> > > 
> > > Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
> > > I Hsin, do you agree?
> > 
> > Sure thing, so do I need to apply the tag myself or we'll follow Yury's
> > patch work?
> 
> I'll send v2 and include your results.

John, FYI.

I Hsing submitted another patch that duplicates this series. You're in
CC, but just in case:

https://lore.kernel.org/all/20250613033447.3531709-1-richard120310@gmail.com/

I think it's pretty disgusting. I will not make him co-author, and
will not give any credit for this work.

Thanks,
Yury

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[I Hsin Cheng]

On Fri, Jun 13, 2025 at 01:13:38AM -0400, Yury Norov wrote:
> > > > > I think Yury submitted the same change here recently:
> > > > >   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> > > > > 
> > > > > Though, I think he has another iteration needed as Thomas had feedback
> > > > > on the subject line.
> > > > > 
> > > > > The bloat-o-meter data is a nice inclusion here!
> > > > > 
> > > > > Yury: Would you be open to adapting I Hsin Cheng's commit message into
> > > > > yours and adding them as co-author via the Co-developed-by: tag?
> > > > > (Assuming I Hsin Cheng agrees - See
> > > > > Documentation/process/submitting-patches.rst for how to do this
> > > > > properly).
> > > > 
> > > > Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
> > > > I Hsin, do you agree?
> > > 
> > > Sure thing, so do I need to apply the tag myself or we'll follow Yury's
> > > patch work?
> > 
> > I'll send v2 and include your results.
> 
> John, FYI.
> 
> I Hsing submitted another patch that duplicates this series. You're in
> CC, but just in case:
> 
> https://lore.kernel.org/all/20250613033447.3531709-1-richard120310@gmail.com/
> 
> I think it's pretty disgusting. I will not make him co-author, and
> will not give any credit for this work.
> 
> Thanks,
> Yury

I'm really sorry for this, I really didn't notice others have already
send the patches.

I didn't mean to copy others work on purpose, I am very sorry.

Thanks,
I Hsin Cheng.

Re: [PATCH] clocksource: Utilize cpumask_next_wrap() to shrink code size

[I Hsin Cheng]

On Fri, Jun 13, 2025 at 01:13:38AM -0400, Yury Norov wrote:
> > > > > I think Yury submitted the same change here recently:
> > > > >   https://lore.kernel.org/lkml/20250607141106.563924-3-yury.norov@gmail.com/
> > > > > 
> > > > > Though, I think he has another iteration needed as Thomas had feedback
> > > > > on the subject line.
> > > > > 
> > > > > The bloat-o-meter data is a nice inclusion here!
> > > > > 
> > > > > Yury: Would you be open to adapting I Hsin Cheng's commit message into
> > > > > yours and adding them as co-author via the Co-developed-by: tag?
> > > > > (Assuming I Hsin Cheng agrees - See
> > > > > Documentation/process/submitting-patches.rst for how to do this
> > > > > properly).
> > > > 
> > > > Yeah, bloat-o-meter report is good enough to add co-developed-by tag.
> > > > I Hsin, do you agree?
> > > 
> > > Sure thing, so do I need to apply the tag myself or we'll follow Yury's
> > > patch work?
> > 
> > I'll send v2 and include your results.
> 
> John, FYI.
> 
> I Hsing submitted another patch that duplicates this series. You're in
> CC, but just in case:
> 
> https://lore.kernel.org/all/20250613033447.3531709-1-richard120310@gmail.com/
> 
> I think it's pretty disgusting. I will not make him co-author, and
> will not give any credit for this work.
> 
> Thanks,
> Yury

I just realized your patch series already does that, I didn't check on
other patches, I'm sorry, I should've been more careful on that, not
just looking at the only patch in the link.

Hope you can forgive me, I really have no offense on that and didn't
mean to do it.

Best regards,
I Hsin Cheng