linux-kernel - Re: [RFC 2/2] x86_64: expand kernel stack to 16K

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Message-ID: <5388A2D9.3080708@zytor.com>
Date:	Fri, 30 May 2014 08:25:13 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dave Chinner <david@...morbit.com>,
	Minchan Kim <minchan@...nel.org>
CC:	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC 2/2] x86_64: expand kernel stack to 16K

On 05/29/2014 06:34 PM, Dave Chinner wrote:
>> ...
>> "kworker/u24:1 (94) used greatest stack depth: 8K bytes left, it means
>> there is some horrible stack hogger in your kernel. Please report it
>> the LKML and enable stacktrace to investigate who is culprit"
> 
> That, however, presumes that a user can reproduce the problem on
> demand. Experience tells me that this is the exception rather than
> the norm for production systems, and so capturing the stack in real
> time is IMO the only useful thing we could add...
> 

If we removed struct thread_info from the stack allocation then one
could do a guard page below the stack.  Of course, we'd have to use IST
for #PF in that case, which makes it a non-production option.

	-hpa


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