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Date: Thu, 29 May 2014 20:06:49 -0400
From: Dave Jones <davej@redhat.com>
Subject: Re: [RFC 2/2] x86_64: expand kernel stack to 16K
Message-ID: <20140530000649.GA3477@redhat.com>
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To: Dave Chinner <david@fromorbit.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Jens Axboe <axboe@kernel.dk>, Minchan Kim <minchan@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, linux-mm <linux-mm@kvack.org>, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>, Rusty Russell <rusty@rustcorp.com.au>, "Michael S. Tsirkin" <mst@redhat.com>, Dave Hansen <dave.hansen@intel.com>, Steven Rostedt <rostedt@goodmis.org>

On Fri, May 30, 2014 at 09:53:08AM +1000, Dave Chinner wrote:

 > That sounds like a plan. Perhaps it would be useful to add a
 > WARN_ON_ONCE(stack_usage > 8k) (or some other arbitrary depth beyond
 > 8k) so that we get some indication that we're hitting a deep stack
 > but the system otherwise keeps functioning. That gives us some
 > motivation to keep stack usage down but isn't a fatal problem like
 > it is now....

We have check_stack_usage() and DEBUG_STACK_USAGE for this.
Though it needs some tweaking if we move to 16K

I gave it a try yesterday, and noticed a spew of noisy warnings as soon
as I gave it a workload to chew on. (Moreso than usual with 8K stacks)

	Dave

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