From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 728F540629D; Mon, 15 Jun 2026 15:38:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781537940; cv=none; b=fpvU/bv9qDmC1XMTpKniI8bnWdXOltYMAdKd7UG0NzeypK4uthizWVBcScLgJKrz5jox2vrv2aYX0SDVurkRdxJOscxh6lfDBDYCLsMV9FInwfmevJ8r+07FZQuUZMkXBiyMWowARhus1oHelEKr3M+794F/U9Bs/7iTNm5mSJc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781537940; c=relaxed/simple; bh=1kCEisoux+0+9v1haZal4lvtQWYoN5DjEzNomtdu0Jw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BDWxmJQ42oM071Yohjs0OJ0wVRaM2myDNNImsDMJINPweIoJ9m6vrXoAFrEF6DRvvInIhNSN+aFYdMVOwntN7aGHVUM+jeMQO0yMbnXwjBZ/vGspziEr39zuQwb3QXZIQKsENsArtMWp4xtU/7bT38XzejTlON0FUXHyxZg/8F0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bwKi9Vni; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bwKi9Vni" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7836A1F00A3A; Mon, 15 Jun 2026 15:38:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781537939; bh=0Yt3bSt3J80NrZsgzpdSkegGuEQYpQIEWrx8GgpDeQA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=bwKi9VniueRjvyn4jM0/pKA7lH0dNxau8VsBz08vm7d+2Nyd1U6Mizs6HdyeMyRju 8hNkeoDuvU245qY793Jm5fL1WEHJ0OcMIv0NKCs17y8onV9bqj+kKk621YmytX5KiO Odz8GVkLW1oZaIDp+mFdqkqhsh4C8rAY4hnffHoAz98gaOP6GEBmC7QGafLel+Mza7 zePfNH8y3+P/QR7zQnDWKjf+1/V60RUVQMxRLtWmr/a0GJTSuc0Afv4WEGSJ3J/2g2 gwBCAGICbSw9fl+ecI8/p4aJau/jB/YKdlcwHhZWgEOmEf3KHv4JIGxwVHFSl8kG54 PimsbdvCbaIpA== Message-ID: <485cc03e-8e96-4b35-9078-19798f01e38c@kernel.org> Date: Mon, 15 Jun 2026 17:38:40 +0200 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) To: "Vlastimil Babka (SUSE)" , Gregory Price Cc: Balbir Singh , lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, longman@redhat.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com, Matthew Wilcox References: <9f1815b0-896b-44ab-9e6d-9316d8f11033@kernel.org> <94d6c446-a8a6-485e-bb3c-ee809ebb1d3b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/15/26 17:27, Vlastimil Babka (SUSE) wrote: > On 6/15/26 17:18, David Hildenbrand (Arm) wrote: >> On 6/15/26 16:38, Vlastimil Babka (SUSE) wrote: >>> >>> I think the memalloc approach is dangerous due to unexpected nesting. There >>> might be nested page allocations in page allocation itself (due to some >>> debugging option). But also interrupts do not change what "current" points >>> to. Suddenly those could start requesting folios and/or private nodes and be >>> surprised, I'm afraid. >> >> Yeah, we'd need some way to distinguish the main allocation from these other >> (nested) allocations. > > That goes against the very principle of scopes. And I don't see how, except > via a ... flag to the main allocation :D Unless we teach the handful of debug callpaths to set a custom context. Have some memalloc_context_save/restore. I'd assume that the number of such nested allocations we can trigger from the buddy (through some callbacks like kasan and such) should be rather limited. I also wonder for a second whether we could use of the _noprof vs. !_noprof mechanism. Essentially, calling a !_noprof variant ("external allocation interface") could mean "save/restore folio allocation". Just a thought. -- Cheers, David