linux-kernel - Re: [PATCH 0/5] Volatile Ranges (v12) & LSF-MM discussion fodder

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Message-ID: <533B4555.3000608@sr71.net>
Date:	Tue, 01 Apr 2014 16:01:41 -0700
From:	Dave Hansen <dave@...1.net>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Johannes Weiner <hannes@...xchg.org>,
	John Stultz <john.stultz@...aro.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Neil Brown <neilb@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mike Hommey <mh@...ndium.org>, Taras Glek <tglek@...illa.com>,
	Jan Kara <jack@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Michel Lespinasse <walken@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 0/5] Volatile Ranges (v12) & LSF-MM discussion fodder

On 04/01/2014 02:35 PM, H. Peter Anvin wrote:
> On 04/01/2014 02:21 PM, Johannes Weiner wrote:
>> Either way, optimistic volatile pointers are nowhere near as
>> transparent to the application as the above description suggests,
>> which makes this usecase not very interesting, IMO.
> 
> ... however, I think you're still derating the value way too much.  The
> case of user space doing elastic memory management is more and more
> common, and for a lot of those applications it is perfectly reasonable
> to either not do system calls or to have to devolatilize first.

The SIGBUS is only in cases where the memory is set as volatile and
_then_ accessed, right?

John, this was something that the Mozilla guys asked for, right?  Any
idea why this isn't ever a problem for them?
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