From: Peter Zijlstra <peterz@infradead.org>
To: "chengjian (D)" <cj.chengjian@huawei.com>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
chenwandun@huawei.com, xiexiuqi@huawei.com, liwei391@huawei.com,
huawei.libin@huawei.com, bobo.shaobowang@huawei.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org
Subject: Re: [PATCH] sched/fair: Optimize select_idle_cpu
Date: Fri, 13 Dec 2019 09:10:33 +0100 [thread overview]
Message-ID: <20191213081033.GZ2844@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <52112146-a4ee-d09f-b61e-9aa35e2e5298@huawei.com>
On Fri, Dec 13, 2019 at 09:51:30AM +0800, chengjian (D) wrote:
> Hi, Peter
>
> I saw the same work in select_idle_core, and I was wondering why the
> per_cpu variable was
>
> needed for this yesterday. Now I think I probably understand : cpumask may
> be too large,
>
> putting it on the stack may cause overflow. Is this correct ?
Yes, for instance when NR_CPUS=4096, struct cpumask ends up being 512
bytes, and that is _far_ too large for an on-stack variable, remember we
have relatively small fixed size stacks.
next prev parent reply other threads:[~2019-12-13 8:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 14:41 [PATCH] sched/fair: Optimize select_idle_cpu Cheng Jian
2019-12-12 14:56 ` chengjian (D)
2019-12-12 15:04 ` Peter Zijlstra
2019-12-13 1:51 ` chengjian (D)
2019-12-13 8:10 ` Peter Zijlstra [this message]
2019-12-12 15:24 ` Peter Zijlstra
2019-12-12 15:44 ` Valentin Schneider
2019-12-13 9:47 ` chengjian (D)
2019-12-13 9:57 ` chengjian (D)
2019-12-13 11:28 ` Valentin Schneider
2019-12-13 12:09 ` Peter Zijlstra
2019-12-13 12:20 ` Valentin Schneider
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