Re: [PATCH v2] powerpc: Warn about use of smt_snooze_delay
Michael Ellerman writes:
> On Tue, 30 Jun 2020 11:29:35 +0930, Joel Stanley wrote:
>> It's not done anything for a long time. Save the percpu variable, and
>> emit a warning to remind users to not expect it to do anything.
>>
>> Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.")
>> Cc: sta...@vger.kernel.org # v3.14
>> Signed-off-by: Joel Stanley
>> --
>> v2:
>> Use pr_warn instead of WARN
>> Reword and print proccess name with pid in message
>> Leave CPU_FTR_SMT test in
>> Add Fixes line
>>
>> [...]
>
> Applied to powerpc/next.
>
> [1/1] powerpc: Warn about use of smt_snooze_delay
>
> https://git.kernel.org/powerpc/c/a02f6d42357acf6e5de6ffc728e6e77faf3ad217
I applied v3 actually.
cheers
Re: [PATCH v2] powerpc: Warn about use of smt_snooze_delay
On Tue, 30 Jun 2020 11:29:35 +0930, Joel Stanley wrote:
> It's not done anything for a long time. Save the percpu variable, and
> emit a warning to remind users to not expect it to do anything.
>
> Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.")
> Cc: sta...@vger.kernel.org # v3.14
> Signed-off-by: Joel Stanley
> --
> v2:
> Use pr_warn instead of WARN
> Reword and print proccess name with pid in message
> Leave CPU_FTR_SMT test in
> Add Fixes line
>
> [...]
Applied to powerpc/next.
[1/1] powerpc: Warn about use of smt_snooze_delay
https://git.kernel.org/powerpc/c/a02f6d42357acf6e5de6ffc728e6e77faf3ad217
cheers
Re: [PATCH v2] powerpc: Warn about use of smt_snooze_delay
On Tue, 4 Aug 2020 at 11:59, Michael Ellerman wrote:
>
> Joel Stanley writes:
> > It's not done anything for a long time. Save the percpu variable, and
> > emit a warning to remind users to not expect it to do anything.
> >
> > Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.")
> > Cc: sta...@vger.kernel.org # v3.14
> > Signed-off-by: Joel Stanley
> > --
> > v2:
> > Use pr_warn instead of WARN
> > Reword and print proccess name with pid in message
> > Leave CPU_FTR_SMT test in
> > Add Fixes line
> >
> > mpe, if you don't agree then feel free to drop the cc stable.
> >
> > Testing 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system it's quite noisy
> > as the online/offline loop that ppc64_cpu runs is slow.
>
> Hmm, that is pretty spammy.
>
> I know I suggested the ratelimit, but I was thinking it would print once
> for each ppc64_cpu invocation, not ~30 times.
>
> How about pr_warn_once(), that should still be sufficient for people to
> notice if they're looking for it.
I think that's a reasonable suggestion.
>
> ...
> > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> > index 571b3259697e..ba6d4cee19ef 100644
> > --- a/arch/powerpc/kernel/sysfs.c
> > +++ b/arch/powerpc/kernel/sysfs.c
> > @@ -32,29 +32,26 @@
> >
> > static DEFINE_PER_CPU(struct cpu, cpu_devices);
> >
> > -/*
> > - * SMT snooze delay stuff, 64-bit only for now
> > - */
> > -
> > #ifdef CONFIG_PPC64
> >
> > -/* Time in microseconds we delay before sleeping in the idle loop */
> > -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 };
> > +/*
> > + * Snooze delay has not been hooked up since 3fa8cad82b94
> > ("powerpc/pseries/cpuidle:
> > + * smt-snooze-delay cleanup.") and has been broken even longer. As was
> > foretold in
> > + * 2014:
> > + *
> > + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to
> > clean
> > + * up the kernel code."
> > + *
> > + * At some point in the future this code should be removed.
> > + */
> >
> > static ssize_t store_smt_snooze_delay(struct device *dev,
> > struct device_attribute *attr,
> > const char *buf,
> > size_t count)
> > {
> > - struct cpu *cpu = container_of(dev, struct cpu, dev);
> > - ssize_t ret;
> > - long snooze;
> > -
> > - ret = sscanf(buf, "%ld", );
> > - if (ret != 1)
> > - return -EINVAL;
> > -
> > - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze;
> > + pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this
> > has no effect\n",
> > + current->comm, current->pid);
>
> Can we make this:
>
> "%s (%d) stored to unsupported smt_snooze_delay, which has no
> effect.\n",
ack
>
>
> > return count;
> > }
> >
> > @@ -62,9 +59,9 @@ static ssize_t show_smt_snooze_delay(struct device *dev,
> >struct device_attribute *attr,
> >char *buf)
> > {
> > - struct cpu *cpu = container_of(dev, struct cpu, dev);
> > -
> > - return sprintf(buf, "%ld\n", per_cpu(smt_snooze_delay, cpu->dev.id));
> > + pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this
> > has no effect\n",
> > + current->comm, current->pid);
>
> It has as much effect as it ever did :)
>
> So maybe:
>
> "%s (%d) read from unsupported smt_snooze_delay.\n",
>
>
> I can do those changes when applying if you like rather than making you
> do a v3.
Yes please! Your suggested changes lgtm.
Cheers,
Joel
Re: [PATCH v2] powerpc: Warn about use of smt_snooze_delay
Joel Stanley writes:
> It's not done anything for a long time. Save the percpu variable, and
> emit a warning to remind users to not expect it to do anything.
>
> Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.")
> Cc: sta...@vger.kernel.org # v3.14
> Signed-off-by: Joel Stanley
> --
> v2:
> Use pr_warn instead of WARN
> Reword and print proccess name with pid in message
> Leave CPU_FTR_SMT test in
> Add Fixes line
>
> mpe, if you don't agree then feel free to drop the cc stable.
>
> Testing 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system it's quite noisy
> as the online/offline loop that ppc64_cpu runs is slow.
Hmm, that is pretty spammy.
I know I suggested the ratelimit, but I was thinking it would print once
for each ppc64_cpu invocation, not ~30 times.
How about pr_warn_once(), that should still be sufficient for people to
notice if they're looking for it.
...
> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index 571b3259697e..ba6d4cee19ef 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -32,29 +32,26 @@
>
> static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> -/*
> - * SMT snooze delay stuff, 64-bit only for now
> - */
> -
> #ifdef CONFIG_PPC64
>
> -/* Time in microseconds we delay before sleeping in the idle loop */
> -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 };
> +/*
> + * Snooze delay has not been hooked up since 3fa8cad82b94
> ("powerpc/pseries/cpuidle:
> + * smt-snooze-delay cleanup.") and has been broken even longer. As was
> foretold in
> + * 2014:
> + *
> + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to
> clean
> + * up the kernel code."
> + *
> + * At some point in the future this code should be removed.
> + */
>
> static ssize_t store_smt_snooze_delay(struct device *dev,
> struct device_attribute *attr,
> const char *buf,
> size_t count)
> {
> - struct cpu *cpu = container_of(dev, struct cpu, dev);
> - ssize_t ret;
> - long snooze;
> -
> - ret = sscanf(buf, "%ld", );
> - if (ret != 1)
> - return -EINVAL;
> -
> - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze;
> + pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this
> has no effect\n",
> + current->comm, current->pid);
Can we make this:
"%s (%d) stored to unsupported smt_snooze_delay, which has no
effect.\n",
> return count;
> }
>
> @@ -62,9 +59,9 @@ static ssize_t show_smt_snooze_delay(struct device *dev,
>struct device_attribute *attr,
>char *buf)
> {
> - struct cpu *cpu = container_of(dev, struct cpu, dev);
> -
> - return sprintf(buf, "%ld\n", per_cpu(smt_snooze_delay, cpu->dev.id));
> + pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this
> has no effect\n",
> + current->comm, current->pid);
It has as much effect as it ever did :)
So maybe:
"%s (%d) read from unsupported smt_snooze_delay.\n",
I can do those changes when applying if you like rather than making you
do a v3.
cheers
Re: [PATCH v2] powerpc: Warn about use of smt_snooze_delay
Hi Joel,
On Tue, Jun 30, 2020 at 11:29:35AM +0930, Joel Stanley wrote:
> It's not done anything for a long time. Save the percpu variable, and
> emit a warning to remind users to not expect it to do anything.
>
> Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.")
> Cc: sta...@vger.kernel.org # v3.14
> Signed-off-by: Joel Stanley
Sorry I missed this v2.
The patch looks good to me.
Acked-by: Gautham R. Shenoy
> --
> v2:
> Use pr_warn instead of WARN
> Reword and print proccess name with pid in message
> Leave CPU_FTR_SMT test in
> Add Fixes line
>
> mpe, if you don't agree then feel free to drop the cc stable.
>
> Testing 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system it's quite noisy
> as the online/offline loop that ppc64_cpu runs is slow.
>
> This could be fixed by open coding pr_warn_ratelimit with the ratelimit
> parameters tweaked if someone was concerned. I'll leave that to someone
> else as a future enhancement.
>
> [ 237.642088][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642175][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642261][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642345][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642430][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642516][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642625][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642709][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642793][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 237.642878][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264030][ T1197] store_smt_snooze_delay: 14 callbacks suppressed
> [ 254.264033][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264048][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264062][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264075][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264089][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264103][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264116][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264130][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264143][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
> [ 254.264157][ T1197] ppc64_cpu (1197) used unsupported smt_snooze_delay,
> this has no effect
>
> Signed-off-by: Joel Stanley
> ---
> arch/powerpc/kernel/sysfs.c | 41 +++--
> 1 file changed, 16 insertions(+), 25 deletions(-)
>
> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index 571b3259697e..ba6d4cee19ef 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -32,29 +32,26 @@
>
> static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> -/*
> - * SMT snooze delay stuff, 64-bit only for now
> - */
> -
> #ifdef CONFIG_PPC64
>
> -/* Time in microseconds we delay before sleeping in the idle loop */
> -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 };
> +/*
> + * Snooze delay has not been hooked up since 3fa8cad82b94
> ("powerpc/pseries/cpuidle:
> + * smt-snooze-delay cleanup.") and has been broken even longer. As was
> foretold in
> + * 2014:
> + *
> + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to
> clean
> + * up the kernel code."
> + *
> + * At some point in the future this code should be removed.
> + */
>
> static ssize_t store_smt_snooze_delay(struct device *dev,
> struct device_attribute *attr,
> const char *buf,
> size_t count)
> {
> - struct cpu *cpu = container_of(dev, struct cpu, dev);
> - ssize_t ret;
> - long snooze;
> -
> - ret = sscanf(buf, "%ld", );
> - if (ret != 1)
> - return -EINVAL;
> -
> - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze;
> + pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this
> has no effect\n",
> + current->comm, current->pid);
> return count;
> }
>
> @@ -62,9 +59,9 @@ static ssize_t show_smt_snooze_delay(struct device *dev,
>struct device_attribute *attr,
>char *buf)
> {
> - struct cpu *cpu
