linux-kernel - Re: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of siblings of SMT

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Message-Id: <4FBE1FAA0200007800085CC4@nat28.tlf.novell.com>
Date:	Thu, 24 May 2012 10:46:50 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Alex Shi" <alex.shi@...el.com>
Cc:	<borislav.petkov@....com>, <arnd@...db.de>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	<akinobu.mita@...il.com>, <eric.dumazet@...il.com>,
	<fweisbec@...il.com>, <rostedt@...dmis.org>, <hughd@...gle.com>,
	<jeremy@...p.org>, <len.brown@...el.com>, <tony.luck@...el.com>,
	<yongjie.ren@...el.com>, <kamezawa.hiroyu@...fujitsu.com>,
	<seto.hidetoshi@...fujitsu.com>, <penberg@...nel.org>,
	<yinghai@...nel.org>, <tglx@...utronix.de>,
	<akpm@...ux-foundation.org>, <ak@...ux.intel.com>, <luto@....edu>,
	<avi@...hat.com>, <dhowells@...hat.com>, <mingo@...hat.com>,
	<riel@...hat.com>, "Rusty Russell" <rusty@...tcorp.com.au>,
	<cpw@....com>, <steiner@....com>, <linux-kernel@...r.kernel.org>,
	<viro@...iv.linux.org.uk>, <hpa@...or.com>
Subject: Re: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of
 siblings of SMT

>>> On 24.05.12 at 11:27, Alex Shi <alex.shi@...el.com> wrote:
> On 05/24/2012 04:42 PM, Peter Zijlstra wrote:
> 
>> On Thu, 2012-05-24 at 16:32 +0800, Alex Shi wrote:
>>> So, I use cpumask_t in stack.
>> 
>> cpumask_t is 512 bytes with NR_CPUS=4096, that's generally considered
>> too big to be on stack.
> 
> 
> I am not consistent with cpumask_t.
> I just want to know why it is too big on stack? Since if it causes
> trouble in using, that mean current kernel will fail to run on 4096 CPU
> system.

Why? Did you spot critical left-over instances of on-stack
cpumask_t-s anywhere?

Jan

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