From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9629C433F5 for ; Tue, 12 Oct 2021 16:50:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3261C60295 for ; Tue, 12 Oct 2021 16:50:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 3261C60295 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id C4C0F940007; Tue, 12 Oct 2021 12:50:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BFD27900002; Tue, 12 Oct 2021 12:50:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AC41B940007; Tue, 12 Oct 2021 12:50:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id 9FDEF900002 for ; Tue, 12 Oct 2021 12:50:46 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 5C791183432D3 for ; Tue, 12 Oct 2021 16:50:46 +0000 (UTC) X-FDA: 78688374492.08.D07B880 Received: from mail-yb1-f176.google.com (mail-yb1-f176.google.com [209.85.219.176]) by imf18.hostedemail.com (Postfix) with ESMTP id DCE9E400208D for ; Tue, 12 Oct 2021 16:50:45 +0000 (UTC) Received: by mail-yb1-f176.google.com with SMTP id v195so69374ybb.0 for ; Tue, 12 Oct 2021 09:50:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Ar09QrWZPbtZ1MPFu1DvBkyuuQRpZh8UgkauKcNPOAM=; b=YaK6rwZTq4aRgarlqFIa1o4IaxOiXPj3qbCjvidENvw68SISlHG+ig7WWufPr7cyyc iLYpsHU9CVkCr3SrnNEDIABH0Rvvra4Y1Toyq7J1Hw07pRZXvbD3xXZu6kqc1t/0riCj XixP30thoEdXn7Fkf4PxSST9mYIrZ9voaWm4ID3wWTwToLSCDjdFU/NMr5IDC54RW4C7 GD6zFsvDMeMJ5L4mc1VIn6D0XScIOUYxYtsXyV2PD9x4hnEfH/EPSldRjaHYwQnzJeD6 ds9Pe3GqsmSNwVDVfAhhG+AElXJLhzNGpKcnTmrpxin8D6FZvzDX5HXboNHhFNyKmoP4 oSfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Ar09QrWZPbtZ1MPFu1DvBkyuuQRpZh8UgkauKcNPOAM=; b=eS+PkzYwbgiBWCQ0gc1sOfzwDm4rmO7aiQqhvDip5esHZmDRuxOJhoWWfqd7Kw+6Mb JkHY0Oro7/x6YPbyqNMskr81DRfmAEt1+8yRL0F2k2ZgATMzqqOpUIZHDyhgC4+9jtxm ziIv+6jwuS14r6NOF9zaJKllHQIbiNWhOBsI4f0RwjXW+wS1wIHy/eygaWVUB//e/tiz 0ADR+8C6QyhDhhbgDAge1Brsgm48508zh2DuPvO2NXxPi3aMtrcaWufKdT5w6J0XBhU8 ERn9mHN6hIGHQwUq+JI1+dPi2ttfn7JpGcOi+LrpqPsnqnEJ88TUDJLEEBJY7a/Euh1y CCOQ== X-Gm-Message-State: AOAM5301YLd5IFT3MLymEJSwiQi6LjFPX8FTxQrBBprQfWBbUu1Kw/8X 7QE0ajVJZYg0Kvt7x0AB3kgwZkGomDMTCeR6t1HCIQ== X-Google-Smtp-Source: ABdhPJz2dtiPou9PSUcVJPjWtl1ZS5oxDJf/t7tSJdJJSiEPO2SLzNa3EVK7YV+ElEwQ813Mhr+Eyk+va9mwyNRAxsc= X-Received: by 2002:a25:d1d3:: with SMTP id i202mr31604897ybg.487.1634057444798; Tue, 12 Oct 2021 09:50:44 -0700 (PDT) MIME-Version: 1.0 References: <202110071111.DF87B4EE3@keescook> <202110081344.FE6A7A82@keescook> In-Reply-To: From: Suren Baghdasaryan Date: Tue, 12 Oct 2021 09:50:33 -0700 Message-ID: Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting To: Michal Hocko Cc: Kees Cook , Pavel Machek , Rasmus Villemoes , David Hildenbrand , John Hubbard , Andrew Morton , Colin Cross , Sumit Semwal , Dave Hansen , Matthew Wilcox , "Kirill A . Shutemov" , Vlastimil Babka , Johannes Weiner , Jonathan Corbet , Al Viro , Randy Dunlap , Kalesh Singh , Peter Xu , rppt@kernel.org, Peter Zijlstra , Catalin Marinas , vincenzo.frascino@arm.com, =?UTF-8?B?Q2hpbndlbiBDaGFuZyAo5by16Yym5paHKQ==?= , Axel Rasmussen , Andrea Arcangeli , Jann Horn , apopple@nvidia.com, Yu Zhao , Will Deacon , fenghua.yu@intel.com, thunder.leizhen@huawei.com, Hugh Dickins , feng.tang@intel.com, Jason Gunthorpe , Roman Gushchin , Thomas Gleixner , krisman@collabora.com, Chris Hyser , Peter Collingbourne , "Eric W. Biederman" , Jens Axboe , legion@kernel.org, Rolf Eike Beer , Cyrill Gorcunov , Muchun Song , Viresh Kumar , Thomas Cedeno , sashal@kernel.org, cxfcosmos@gmail.com, LKML , linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm , kernel-team , Tim Murray Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DCE9E400208D X-Stat-Signature: 6cumkjatdw8ipyhn66wp4dgydr4ge1zt Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=YaK6rwZT; spf=pass (imf18.hostedemail.com: domain of surenb@google.com designates 209.85.219.176 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1634057445-153268 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 12, 2021 at 12:37 AM Michal Hocko wrote: > > On Mon 11-10-21 18:20:25, Suren Baghdasaryan wrote: > > On Mon, Oct 11, 2021 at 6:18 PM Suren Baghdasaryan wrote: > > > > > > On Mon, Oct 11, 2021 at 1:36 AM Michal Hocko wrote: > > > > > > > > On Fri 08-10-21 13:58:01, Kees Cook wrote: > > > > > - Strings for "anon" specifically have no required format (this is good) > > > > > it's informational like the task_struct::comm and can (roughly) > > > > > anything. There's no naming convention for memfds, AF_UNIX, etc. Why > > > > > is one needed here? That seems like a completely unreasonable > > > > > requirement. > > > > > > > > I might be misreading the justification for the feature. Patch 2 is > > > > talking about tools that need to understand memeory usage to make > > > > further actions. Also Suren was suggesting "numbering convetion" as an > > > > argument against. > > > > > > > > So can we get a clear example how is this being used actually? If this > > > > is just to be used to debug by humans than I can see an argument for > > > > human readable form. If this is, however, meant to be used by tools to > > > > make some actions then the argument for strings is much weaker. > > > > > > The simplest usecase is when we notice that a process consumes more > > > memory than usual and we do "cat /proc/$(pidof my_process)/maps" to > > > check which area is contributing to this growth. The names we assign > > > to anonymous areas are descriptive enough for a developer to get an > > > idea where the increased consumption is coming from and how to proceed > > > with their investigation. > > > There are of course cases when tools are involved, but the end-user is > > > always a human and the final report should contain easily > > > understandable data. > > OK, it would have been much more preferable to be explicit about this > main use case from the very beginning. Just to make sure we are at the > same page. Is the primary usecase usage and bug reporting? Sorry, I should have spent more time on patch #2 description. Yes, debugging memory issues is the primary usecase. In fact that's the only usecase in Android AFAIK. > > My initial understanding was that at userspace managed memory management > could make an educated guess about targeted reclaim (e.g. MADV_{FREE,COLD,PAGEOUT} > for cached data in memory like uncompressed images/data). Such a usecase > would clearly require a standardized id/naming convention to be > application neutral. Ah, now I understand your angle. Our prior work on process_madvise() probably helped in leading your thoughts in this direction :) Sorry about the confusion. > > > > IIUC, the main argument here is whether the userspace can provide > > > tools to perform the translations between ids and names, with the > > > kernel accepting and reporting ids instead of strings. Technically > > > it's possible, but to be practical that conversion should be fast > > > because we will need to make name->id conversion potentially for each > > > mmap. On the consumer side the performance is not as critical, but the > > > fact that instead of dumping /proc/$pid/maps we will have to parse the > > > file, do id->name conversion and replace all [anon:id] with > > > [anon:name] would be an issue when we do that in bulk, for example > > > when collecting system-wide data for a bugreport. > > Whether you use ids or human readable strings you still have to > understand the underlying meaning to make any educated guess. Let me > give you an example. Say I have an application with a memory leak. Right > now I can only tell that it is anonymous memory growing but it is not > clear who uses that anonymous. You are adding a means to tell different > users appart. That is really helpful. Now I know this is an anon > user 1234 or MySuperAnonMemory. Neither of the will not tell me more > without a id/naming convention or reading the code. A convention can be > useful for the most common users (e.g. a specific allocator) but I am > rather dubious there are many more that would be _generally_ recognized > without some understanding of the said application. I guess an example would be better to clarify this. Here are some vma names from Google maps app: [anon:dalvik-main space (region space)] [anon:dalvik-/apex/com.android.art/javalib/boot.art] [anon:dalvik-/apex/com.android.art/javalib/boot-apache-xml.art] [anon:.bss] [anon:dalvik-zygote space] [anon:dalvik-non moving space] [anon:dalvik-free list large object space] [anon:dalvik-/product/app/Maps/oat/arm64/Maps.art] [anon:stack_and_tls:20792] [anon:stack_and_tls:20791] [anon:dalvik-LinearAlloc] [anon:dalvik-CompilerMetadata] [anon:dalvik-indirect ref table] [anon:dalvik-live stack] [anon:dalvik-allocation stack] [anon:dalvik-large object free list space allocation info map] [anon:scudo:primary] [anon:scudo:secondary] [anon:bionic_alloc_small_objects] Most of them have names standard for Android and can be recognized by developers and even Android framework (example where "anon:dalvik-main space" and other standard names are being parsed: https://cs.android.com/android/platform/superproject/+/master:frameworks/base/core/jni/android_os_Debug.cpp;l=340). Names like "anon:dalvik-/apex/com.android.art/javalib/boot.art" help the developer to recognize the component responsible for the memory. Names like "anon:stack_and_tls:20792" include the TID of the thread which uses this memory. All this information can help in narrowing down memory consumption investigation. Hopefully these examples clarify the usage a bit better? > > Maybe the situation in Android is different because the runtime is more > coupled but is it reasonable to expect any common naming conventions for > general Linux platforms? Well, to be useful the system would have to agree to *some* convention I guess. > > I am slightly worried that we have spent way too much time talking > specifics about id->name translation rather than the actual usability > of the token. Agree. I'll try to avoid further confusions. Thanks! > -- > Michal Hocko > SUSE Labs