From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx197.postini.com [74.125.245.197]) by kanga.kvack.org (Postfix) with SMTP id 2EED36B0032 for ; Fri, 12 Jul 2013 05:15:12 -0400 (EDT) Received: by mail-ea0-f170.google.com with SMTP id h10so6166919eaj.15 for ; Fri, 12 Jul 2013 02:15:10 -0700 (PDT) Date: Fri, 12 Jul 2013 11:15:06 +0200 From: Ingo Molnar Subject: Re: [PATCH 2/2] mm: add a field to store names for private anonymous memory Message-ID: <20130712091506.GA5315@gmail.com> References: <1373596462-27115-1-git-send-email-ccross@android.com> <1373596462-27115-2-git-send-email-ccross@android.com> <51DF9682.9040301@kernel.org> <20130712081348.GM25631@dyad.programming.kicks-ass.net> <20130712081717.GN25631@dyad.programming.kicks-ass.net> <20130712084406.GB4328@gmail.com> <20130712090046.GP25631@dyad.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130712090046.GP25631@dyad.programming.kicks-ass.net> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Pekka Enberg , Colin Cross , linux-kernel@vger.kernel.org, Kyungmin Park , Christoph Hellwig , John Stultz , "Eric W. Biederman" , Dave Hansen , Rob Landley , Andrew Morton , Cyrill Gorcunov , David Rientjes , Davidlohr Bueso , Kees Cook , Al Viro , Hugh Dickins , Mel Gorman , Michel Lespinasse , Rik van Riel , Konstantin Khlebnikov , "Paul E. McKenney" , David Howells , Arnd Bergmann , Dave Jones , "Rafael J. Wysocki" , Oleg Nesterov , Shaohua Li , Sasha Levin , KOSAKI Motohiro , Johannes Weiner , linux-doc@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds * Peter Zijlstra wrote: > On Fri, Jul 12, 2013 at 10:44:06AM +0200, Ingo Molnar wrote: > > It makes tons of sense. > > > > Just like we have a task's cmd-name it makes a lot of sense to name > > objects in a human readable fashion, to help debugging, instrumentation, > > performance analysis, etc. > > > > Yes, in theory user-space could do all that. That's not the point: the > > point is to make it fast, easy enough and to have a central version (the > > kernel). > > > > Doing it via temporary files has various disadvantages: > > We need those files anyway.. The current proposal is that the entire VMA > has a single userspace pointer in it. Or rather a 64bit value. Yes but accessible via /proc//mem or so? > > I guess the real question is not whether it's useful, I think it > > clearly is. The question should be: are there real downsides? Does the > > addition to the anon mmap field blow up the size of vma_struct by a > > pointer, or is there still space? > > I don't see how the single u64 is useful at all for perf; you can have > at most one u64 per page; that's not nearly enough to put symbol > information in. Therefore we still require external files. I was thinking about it in the context of its original purpose: naming heap areas, which are pretty anonymous right now - /proc/*/maps is full of mystery ranges today. It's indeed not good enough for finer grained structure. Thanks, Ingo -- 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