From: Thomas Gleixner <tglx@linutronix.de>
To: Yury Norov <yury.norov@gmail.com>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Frederic Weisbecker <frederic@kernel.org>,
Imran Khan <imran.f.khan@oracle.com>,
Ingo Molnar <mingo@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Juri Lelli <juri.lelli@redhat.com>,
Leonardo Bras <leobras@redhat.com>, Mel Gorman <mgorman@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
Rik van Riel <riel@surriel.com>,
Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>,
Valentin Schneider <vschneid@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Waiman Long <longman@redhat.com>,
Yury Norov <yury.norov@gmail.com>,
Zefan Li <lizefan.x@bytedance.com>,
cgroups@vger.kernel.org
Subject: Re: [PATCH 3/6] driver core: cpu: optimize print_cpus_isolated()
Date: Tue, 14 May 2024 23:02:00 +0200 [thread overview]
Message-ID: <87jzjwkszb.ffs@tglx> (raw)
In-Reply-To: <20240513220146.1461457-4-yury.norov@gmail.com>
On Mon, May 13 2024 at 15:01, Yury Norov wrote:
> The function may be called with housekeeping_cpumask == cpu_possible_mask,
How so? There is no cpumask argument in the function signature. Can you
please be precise?
> and in such case the 'isolated' cpumask would be just empty.
>
> We can call cpumask_clear() in that case, and save CPU cycles.
>
> @@ -282,8 +282,10 @@ static ssize_t print_cpus_isolated(struct device *dev,
> if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
> return -ENOMEM;
>
> - cpumask_andnot(isolated, cpu_possible_mask,
> - housekeeping_cpumask(HK_TYPE_DOMAIN));
> + if (cpu_possible_mask != housekeeping_cpumask(HK_TYPE_DOMAIN))
> + cpumask_andnot(isolated, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOMAIN));
> + else
> + cpumask_clear(isolated);
> len = sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(isolated));
>
> free_cpumask_var(isolated);
Seriously? You need clear() to emit an empty string via %*pbl?
if (cpu_possible_mask != housekeeping_cpumask(HK_TYPE_DOMAIN)) {
if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
return -ENOMEM;
cpumask_andnot(isolated, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOMAIN));
len = sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(isolated));
free_cpumask_var(isolated);
} else {
len = sysfs_emit(buf, "\n");
}
That actually would make sense and spare way more CPU cycles, no?
Is it actually worth the larger text size? Not really convinced about that.
Thanks,
tglx
next prev parent reply other threads:[~2024-05-14 21:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-13 22:01 [PATCH 0/6] bitmap: optimize API usage Yury Norov
2024-05-13 22:01 ` [PATCH 1/6] smp: optimize smp_call_function_many_cond() Yury Norov
2024-05-13 22:01 ` [PATCH 2/6] sched/topology: optimize topology_span_sane() Yury Norov
2024-05-14 20:53 ` Christophe JAILLET
2024-05-13 22:01 ` [PATCH 3/6] driver core: cpu: optimize print_cpus_isolated() Yury Norov
2024-05-14 21:02 ` Thomas Gleixner [this message]
2024-05-13 22:01 ` [PATCH 4/6] genirq: optimize irq_do_set_affinity() Yury Norov
2024-05-14 12:51 ` Jinjie Ruan
2024-05-14 16:16 ` Yury Norov
2024-05-13 22:01 ` [PATCH 5/6] cgroup/cpuset: optimize cpuset_mems_allowed_intersects() Yury Norov
2024-05-14 16:47 ` Waiman Long
2024-05-14 16:50 ` Tejun Heo
2024-05-14 16:55 ` Waiman Long
2024-05-13 22:01 ` [PATCH 6/6] tick/common: optimize cpumask_equal() usage Yury Norov
2024-05-14 8:31 ` Thomas Gleixner
2024-05-14 8:42 ` Thomas Gleixner
2024-05-14 16:47 ` Yury Norov
2024-05-14 20:47 ` Thomas Gleixner
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