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 0E893C433EF for ; Tue, 12 Oct 2021 17:01:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 95D8960E53 for ; Tue, 12 Oct 2021 17:01:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 95D8960E53 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 2CB01940007; Tue, 12 Oct 2021 13:01:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 27A41900002; Tue, 12 Oct 2021 13:01:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 14223940007; Tue, 12 Oct 2021 13:01:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0097.hostedemail.com [216.40.44.97]) by kanga.kvack.org (Postfix) with ESMTP id 06688900002 for ; Tue, 12 Oct 2021 13:01:18 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id A9326183EC598 for ; Tue, 12 Oct 2021 17:01:17 +0000 (UTC) X-FDA: 78688400994.24.21C0DD3 Received: from mail-yb1-f174.google.com (mail-yb1-f174.google.com [209.85.219.174]) by imf28.hostedemail.com (Postfix) with ESMTP id 51F5490000AC for ; Tue, 12 Oct 2021 17:01:17 +0000 (UTC) Received: by mail-yb1-f174.google.com with SMTP id z5so51382ybj.2 for ; Tue, 12 Oct 2021 10:01:17 -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=8Tzhl0MVFy9A0j1rnPsvy8YVR9B6G5UsH8EyCGPBclE=; b=ZcOenQ6fVRLLsv/XeQFPg7fnM5YEM500n89LF22NH+zpMwjIeByGZnUmUhodoBeu4+ uwRWuao0Tu++R3OlxtP+LKtt7vSGIzR7JzZAOoRYt2nrsggm63sKqt5bHG4YydOI6rbz EWfFpyddnUNjAcDMQdF8LgCWLuUDazezQTw7gQy9qtJAntsZUsYobnzegylDiaOMGwOI MDxq8+Dre7QZRyI4jvrs5HJwdVG78mh5+2eIvdkY04GLC9IKL1K9rD+9U39CrRpRZfZ+ 85bzsQZhzLNXmWkU4iZojVd4u4SE2SIV3Kygv4OxuhiD5x9Uo9VVm0sv7jo2p7b5oW5u 1ctg== 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=8Tzhl0MVFy9A0j1rnPsvy8YVR9B6G5UsH8EyCGPBclE=; b=QbKVbTrrrwv0fnMWv1TezSHj7YjM6oh6hZRfKX7A4bjoJnz0qhRd5rqWniULg778Q/ hN8U+RGUJuP6oIA02m54Gai1qD5PC9PeYfflzsyGRkcctd5Hi86yfBvfk8c37oqCRw5r 7QZKkln5NttguGZLmZHXIYZ33x90Ljm1hPlR0o3nuj119KDVIiMVF9JodQsV4UZJATi0 Wyms6P4KRlrPO7qt0BAyZM0f2IQ3E3ZMrPAY6iaODREpyj6hkZMPZYTInRJhJ9KGAMx+ 0iyInN6fwQN4lDso6MtQuwe6PgPSobylNO9UbyJc4QJNeX8ITINmxcoLR8jG89qAP/+7 4zmg== X-Gm-Message-State: AOAM533p6IM8KCEQmyse+Ub8WGI35I1/qeNiDIbR32TsVLzPIm2aSiDC lwjGBr7zio+f4wKer9InRC0vjbXe21nXndGxWZ/CWA== X-Google-Smtp-Source: ABdhPJwOPTX5trcDK3fnE5j1KylJQjqxL9bNX71uZKloGBWhRHQA8xA+zeQh1Ynbd9I628/FnTZxa/rbysY+VRcBD8Y= X-Received: by 2002:a25:552:: with SMTP id 79mr28537708ybf.202.1634058076286; Tue, 12 Oct 2021 10:01:16 -0700 (PDT) MIME-Version: 1.0 References: <92cbfe3b-f3d1-a8e1-7eb9-bab735e782f6@rasmusvillemoes.dk> <20211007101527.GA26288@duo.ucw.cz> <202110071111.DF87B4EE3@keescook> <202110081344.FE6A7A82@keescook> <26f9db1e-69e9-1a54-6d49-45c0c180067c@redhat.com> In-Reply-To: <26f9db1e-69e9-1a54-6d49-45c0c180067c@redhat.com> From: Suren Baghdasaryan Date: Tue, 12 Oct 2021 10:01:05 -0700 Message-ID: Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting To: David Hildenbrand Cc: Michal Hocko , Kees Cook , Pavel Machek , Rasmus Villemoes , 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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 51F5490000AC X-Stat-Signature: 31orc7y8e45b1dj8x3h8fqnieqjtn78c Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ZcOenQ6f; spf=pass (imf28.hostedemail.com: domain of surenb@google.com designates 209.85.219.174 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1634058077-146930 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 12:44 AM David Hildenbrand wrote: > > > I'm still evaluating the proposal to use memfds but I'm not sure if > > the issue that David Hildenbrand mentioned about additional memory > > consumed in pagecache (which has to be addressed) is the only one we > > will encounter with this approach. If anyone knows of any potential > > issues with using memfds as named anonymous memory, I would really > > appreciate your feedback before I go too far in that direction. > > [MAP_PRIVATE memfd only behave that way with 4k, not with huge pages, so > I think it just has to be fixed. It doesn't make any sense to allocate a > page for the pagecache ("populate the file") when accessing via a > private mapping that's supposed to leave the file untouched] > > My gut feeling is if you really need a string as identifier, then try > going with memfds. Yes, we might hit some road blocks to be sorted out, > but it just logically makes sense to me: Files have names. These names > exist before mapping and after mapping. They "name" the content. I'm investigating this direction. I don't have much background with memfds, so I'll need to digest the code first. > > Maybe it's just me, but the whole interface, setting the name via a > prctl after the mapping was already instantiated doesn't really spark > joy at my end. That's not a strong pushback, but if we can avoid it > using something that's already there, that would be very much preferred. Actually that's one of my worries about using memfds. There might be cases when we need to name a vma after it was mapped. memfd_create() would not allow us to do that AFAIKT. But I need to check all usages to say if that's really an issue. Thanks! > > -- > Thanks, > > David / dhildenb > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >