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Message-ID: <877cfsjf0q.ffs@tglx>
Date: Fri, 17 May 2024 23:37:57 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Costa Shulyupin <costa.shul@...hat.com>, longman@...hat.com,
pauld@...hat.com, juri.lelli@...hat.com, prarit@...hat.com,
vschneid@...hat.com, Anna-Maria Behnsen <anna-maria@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>, Zefan Li
<lizefan.x@...edance.com>, Tejun Heo <tj@...nel.org>, Johannes Weiner
<hannes@...xchg.org>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra
<peterz@...radead.org>, 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>, Daniel Bristot de Oliveira <bristot@...hat.com>, Petr
Mladek <pmladek@...e.com>, Andrew Morton <akpm@...ux-foundation.org>,
Masahiro Yamada <masahiroy@...nel.org>, Randy Dunlap
<rdunlap@...radead.org>, Yoann Congal <yoann.congal@...le.fr>, "Gustavo A.
R. Silva" <gustavoars@...nel.org>, Nhat Pham <nphamcs@...il.com>, Costa
Shulyupin <costa.shul@...hat.com>, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org
Subject: Re: [PATCH v1 1/7] sched/isolation: Add infrastructure to adjust
affinity for dynamic CPU isolation
On Thu, May 16 2024 at 22:04, Costa Shulyupin wrote:
> Introduce infrastructure function housekeeping_update() to change
> housekeeping_cpumask during runtime and adjust affinities of depended
> subsystems.
>
> Affinity adjustments of subsystems follow in subsequent patches.
>
> Parent patch:
> "sched/isolation: Exclude dynamically isolated CPUs from housekeeping masks"
> https://lore.kernel.org/lkml/20240229021414.508972-2-longman@redhat.com/
>
> Test example for cgroup2:
>
> cd /sys/fs/cgroup/
> echo +cpuset > cgroup.subtree_control
> mkdir test
> echo isolated > test/cpuset.cpus.partition
> echo $isolate > test/cpuset.cpus
This changelog is not telling me anything. Please see
Documentation/process/ what changelogs should contain.
> +/*
> + * housekeeping_update - change housekeeping.cpumasks[type] and propagate the
> + * change.
> + *
> + * Assuming cpuset_mutex is held in sched_partition_write or
> + * cpuset_write_resmask.
Locking cannot be assumed. lockdep_assert_held() is there to document
and enforce such requirements.
> + */
> +static int housekeeping_update(enum hk_type type, cpumask_var_t update)
Please us 'struct cpumask *update' as it makes it clear what this is
about. cpumask_var_t is a hack to make onstack and embedded cpumask and
their allocated counterparts possible without #ifdeffery in the code.
But any function which is not related to alloc/free of cpumask_var_t
should simply use 'struct cpumask *' as argument type.
> + housekeeping.flags |= BIT(type);
The existing code uses WRITE_ONCE() probably for a reason. Why is that
not longer required here?
> static int __init housekeeping_setup(char *str, unsigned long flags)
> {
> cpumask_var_t non_housekeeping_mask, housekeeping_staging;
> @@ -314,9 +347,12 @@ int housekeeping_exlude_isolcpus(const struct cpumask *isolcpus, unsigned long f
> /*
> * Reset housekeeping to bootup default
> */
> - for_each_set_bit(type, &housekeeping_boot.flags, HK_TYPE_MAX)
> - cpumask_copy(housekeeping.cpumasks[type],
> - housekeeping_boot.cpumasks[type]);
> + for_each_set_bit(type, &housekeeping_boot.flags, HK_TYPE_MAX) {
> + int err = housekeeping_update(type, housekeeping_boot.cpumasks[type]);
> +
> + if (err)
> + return err;
> + }
>
> WRITE_ONCE(housekeeping.flags, housekeeping_boot.flags);
> if (!housekeeping_boot.flags &&
> @@ -344,9 +380,11 @@ int housekeeping_exlude_isolcpus(const struct cpumask *isolcpus, unsigned long f
> cpumask_andnot(tmp_mask, src_mask, isolcpus);
> if (!cpumask_intersects(tmp_mask, cpu_online_mask))
> return -EINVAL; /* Invalid isolated CPUs */
> - cpumask_copy(housekeeping.cpumasks[type], tmp_mask);
> + int err = housekeeping_update(type, tmp_mask);
> +
> + if (err)
> + return err;
Do we really need two places to define 'int err' or might it be possible
to have one instance defined at function scope?
Thanks,
tglx
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