From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f181.google.com (mail-pf0-f181.google.com [209.85.192.181]) by kanga.kvack.org (Postfix) with ESMTP id 7CBE46B0005 for ; Wed, 20 Jan 2016 00:27:46 -0500 (EST) Received: by mail-pf0-f181.google.com with SMTP id e65so188625928pfe.0 for ; Tue, 19 Jan 2016 21:27:46 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id yq2si12587968pac.19.2016.01.19.21.27.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Jan 2016 21:27:45 -0800 (PST) Date: Tue, 19 Jan 2016 21:27:45 -0800 From: Andrew Morton Subject: Re: [PATCH] proc: revert /proc//maps [stack:TID] annotation Message-Id: <20160119212745.eee310f5.akpm@linux-foundation.org> In-Reply-To: References: <1453226559-17322-1-git-send-email-hannes@cmpxchg.org> <20160119141430.8ff9c464.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Siddhesh Poyarekar Cc: Johannes Weiner , Shaohua Li , linux-mm@kvack.org, linux-kernel , kernel-team@fb.com On Wed, 20 Jan 2016 08:47:39 +0530 Siddhesh Poyarekar wrote: > On 20 January 2016 at 03:44, Andrew Morton wrote: > > Any thoughts on the obvious back-compatibility concerns? ie, why did > > Siddhesh implement this in the first place? My bad for not ensuring > > that the changelog told us this. > > > > https://lkml.org/lkml/2012/1/14/25 has more info: > > > > : Memory mmaped by glibc for a thread stack currently shows up as a > > : simple anonymous map, which makes it difficult to differentiate between > > : memory usage of the thread on stack and other dynamic allocation. > > : Since glibc already uses MAP_STACK to request this mapping, the > > : attached patch uses this flag to add additional VM_STACK_FLAGS to the > > : resulting vma so that the mapping is treated as a stack and not any > > : regular anonymous mapping. Also, one may use vm_flags to decide if a > > : vma is a stack. > > > > But even that doesn't really tell us what the actual *value* of the > > patch is to end-users. > > The end users needed a way to identify thread stacks programmatically > and there wasn't a way to do that. I'm afraid I no longer remember > (or have access to the resources that would aid my memory since I > changed employers) the details of their requirement. However, I did > do this on my own time because I thought it was an interesting project > for me and nobody really gave any feedback then as to its utility, so > as far as I am concerned you could roll back the main thread maps > information since the information is available in the thread-specific > files. OK, thanks. I was thinking of queueing this for 4.6 to let it bake in -next for a cycle, but quadratic performance is bad and nobody will test such an obscure feature in -next so maybe I'll jam it into 4.5 and we wait and see. -- 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