From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Josh Boyer <jwboyer@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Boyer <jwboyer@fedoraproject.org>,
Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [GIT PULL] core kernel update
Date: Tue, 19 Nov 2013 20:14:34 +0100 [thread overview]
Message-ID: <20131119191434.GQ16796@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20131119190904.GA22076@gmail.com>
On Tue, Nov 19, 2013 at 08:09:04PM +0100, Ingo Molnar wrote:
> The actual value of the limit - here's the on-stack cpumask sizes of
> the candidate range:
>
> 128 CPUs: 16 byte cpumasks
> 256 CPUs: 32 byte cpumasks
> 512 CPUs: 64 byte cpumasks
So 512 / 64bytes is a single cacheline and feels like a nice cut-off
before requiring an extra indirection and more cachelines.
64 bytes also doesn't sound _that_ big to have on-stack.
So I'd go for having the cut-off on >512, unless of course theres
evidence 64bytes is already too much.
next prev parent reply other threads:[~2013-11-19 19:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-19 15:42 Ingo Molnar
2013-11-19 18:47 ` Linus Torvalds
2013-11-19 19:09 ` Ingo Molnar
2013-11-19 19:14 ` Peter Zijlstra [this message]
2013-11-19 19:18 ` Ingo Molnar
2013-11-19 19:18 ` Linus Torvalds
2013-11-19 23:05 ` Rusty Russell
2013-11-20 11:50 ` Ingo Molnar
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