linux-kernel - Re: [PATCH] sched/cpuacct: show only present CPUs to userspace

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Message-ID: <CAEivzxdUC=R1oTdrwRDdrfdU7AUcRdTQum_cUUt__Zvi6xr+3w@mail.gmail.com>
Date: Fri, 25 Oct 2024 17:35:56 +0200
From: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: mingo@...hat.com
Cc: James Morse <james.morse@....com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
	Gavin Shan <gshan@...hat.com>, "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, 
	Thomas Gleixner <tglx@...utronix.de>, Simon Deziel <simon.deziel@...onical.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/cpuacct: show only present CPUs to userspace

Gentle ping.

On Thu, Oct 17, 2024 at 12:22 PM Alexander Mikhalitsyn
<aleksandr.mikhalitsyn@...onical.com> wrote:
>
> After commit b0c69e1214bc ("drivers: base: Use present CPUs in GENERIC_CPU_DEVICES")
> changed which CPUs are shown in /sys/devices/system/cpu/ (only "present" ones)
> it also makes sense to change cpuacct cgroupv1 code not to report CPUs
> which are not present in the system as it confuses userspace.
> Let's make it consistent.
>
> A configuration when #(present CPUs) < #(possible CPUs) is easy to get with:
> qemu-system-x86_64
>         -smp 3,maxcpus=12 \
>         ...
>
> Cc: James Morse <james.morse@....com>
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Cc: Gavin Shan <gshan@...hat.com>
> Cc: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Reported-by: Simon Deziel <simon.deziel@...onical.com>
> Closes: https://github.com/canonical/lxd/issues/13324
> Co-developed-by: Simon Deziel <simon.deziel@...onical.com>
> Signed-off-by: Simon Deziel <simon.deziel@...onical.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
>  kernel/sched/cpuacct.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
> index 0de9dda09949..0f07fbfdb20e 100644
> --- a/kernel/sched/cpuacct.c
> +++ b/kernel/sched/cpuacct.c
> @@ -213,7 +213,7 @@ static int __cpuacct_percpu_seq_show(struct seq_file *m,
>         u64 percpu;
>         int i;
>
> -       for_each_possible_cpu(i) {
> +       for_each_present_cpu(i) {
>                 percpu = cpuacct_cpuusage_read(ca, i, index);
>                 seq_printf(m, "%llu ", (unsigned long long) percpu);
>         }
> @@ -247,7 +247,7 @@ static int cpuacct_all_seq_show(struct seq_file *m, void *V)
>                 seq_printf(m, " %s", cpuacct_stat_desc[index]);
>         seq_puts(m, "\n");
>
> -       for_each_possible_cpu(cpu) {
> +       for_each_present_cpu(cpu) {
>                 seq_printf(m, "%d", cpu);
>                 for (index = 0; index < CPUACCT_STAT_NSTATS; index++)
>                         seq_printf(m, " %llu",
> --
> 2.34.1
>