From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx195.postini.com [74.125.245.195]) by kanga.kvack.org (Postfix) with SMTP id F32B26B0002 for ; Tue, 23 Apr 2013 20:26:53 -0400 (EDT) Received: by mail-pd0-f178.google.com with SMTP id w10so235614pde.23 for ; Tue, 23 Apr 2013 17:26:53 -0700 (PDT) Message-ID: <517726C8.4030207@linaro.org> Date: Tue, 23 Apr 2013 17:26:48 -0700 From: John Stultz MIME-Version: 1.0 Subject: Re: Summary of LSF-MM Volatile Ranges Discussion References: <516EE256.2070303@linaro.org> <5175FBEB.4020809@linaro.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dmitry Vyukov Cc: lsf@lists.linux-foundation.org, linux-mm@kvack.org, Minchan Kim , Paul Turner , Robert Love , Dave Hansen , Taras Glek , Mike Hommey , Kostya Serebryany , Hugh Dickins , Michel Lespinasse , KOSAKI Motohiro , Johannes Weiner , gthelen@google.com, Rik van Riel , glommer@parallels.com, mhocko@suse.de On 04/22/2013 11:51 PM, Dmitry Vyukov wrote: > Just want to make sure our case does not fall out of the discussion: > https://code.google.com/p/thread-sanitizer/wiki/VolatileRanges Yes, while I forgot to mention it in the summary, I did bring it up briefly, but I cannot claim to have done it justice. Personally, while I suspect we might be able to support your desired semantics (ie: mark once volatile, always zero-fill, no sigbus) via a mode flag > While reading your email, I remembered that we actually have some > pages mapped from a file inside the range. So it's like 70TB of ANON > mapping + few pages in the middle mapped from FILE. The file is mapped > with MAP_PRIVATE + PROT_READ, it's read-only and not shared. > But we want to mark the volatile range only once on startup, so > performance is not a serious concern (while the function in executed > in say no more than 10ms). > If the mixed ANON+FILE ranges becomes a serious problem, we are ready > to remove FILE mappings, because it's only an optimization. I.e. we > can make it pure ANON mapping. Well, in my mind, the MAP_PRIVATE mappings are semantically the same as anonymous memory with regards to volatility. So I hope this wouldn't be an issue. thanks -john -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org