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X-CSE-ConnectionGUID: 2vKrvukASA2vWgd9ybsgkA== X-CSE-MsgGUID: yfU9ZmGPQN+ZU1ottmC2XQ== X-IronPort-AV: E=McAfee;i="6700,10204,11262"; a="57608214" X-IronPort-AV: E=Sophos;i="6.12,170,1728975600"; d="scan'208";a="57608214" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2024 11:16:05 -0800 X-CSE-ConnectionGUID: 6uwrWOb8QsmRBRQNFKzWPw== X-CSE-MsgGUID: 056/sa7STnqg1YzmOmukiw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,170,1728975600"; d="scan'208";a="89591297" Received: from tassilo.jf.intel.com (HELO tassilo) ([10.54.38.190]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2024 11:16:04 -0800 Date: Wed, 20 Nov 2024 11:14:49 -0800 From: Andi Kleen To: Pasha Tatashin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, derek.kiernan@amd.com, dragan.cvetic@amd.com, arnd@arndb.de, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, shuah@kernel.org, vegard.nossum@oracle.com, vattunuru@marvell.com, schalla@marvell.com, david@redhat.com, willy@infradead.org, osalvador@suse.de, usama.anjum@collabora.com, andrii@kernel.org, ryan.roberts@arm.com, peterx@redhat.com, oleg@redhat.com Subject: Re: [RFCv1 0/6] Page Detective Message-ID: References: <20241116175922.3265872-1-pasha.tatashin@soleen.com> <87wmgxvs81.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Stat-Signature: nks7rz7m4u7r76jp81iez1k3e4fq5ngj X-Rspamd-Queue-Id: 7A3248001C X-Rspam-User: X-HE-Tag: 1732130068-33718 X-HE-Meta: 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 hniYRlup B02hGHAaxU3ckUwSd7+fBfYgzxp1uC0JEDK5GrHW6d/3RIWHTE4JYjzzzzysFCLRDHCPZ216PxMqYsrReEFtvqJPuurbspChSglS2OWAD1WD1FL+CoRNWfcGFUsZla+N2V19ZpdX9B/vftWL8Owhre39tzZfVPxtRcptnGxUi/Udd70mcgHbf0hdFtA== 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: List-Subscribe: List-Unsubscribe: > - Quickly identify all user processes mapping a given page. Can be done with /proc/*/pagemap today. Maybe it's not "quick" because it won't use the rmap chains, but is that a serious issue? > - Determine if and where the kernel maps the page, which is also > important given the opportunity to remove guest memory from the kernel > direct map (as discussed at LPC'24). At least x86 already has a kernel page table dumper in debugfs that can be used for this. The value of a second redundant one seems low. > We also plan to extend this functionality to include KVM and IOMMU > page tables in the future. Yes dumpers for those would likely be useful. (at least for the case when one hand is tied behind your back by security policies forbidding /proc/kcore access) > provides an interface to traversing through user page > tables, but the other information cannot be extracted using the > existing interfaces. Like what? You mean the reference counts? /proc/k* doesn't have any reference counts, and no space for full counts, but I suspect usually all you need to know is a few states like (>1, 1, 0, maybe negative) which could be mapped to a few spare kpageflags bits. That said I thought Willy wanted to move a lot of these elsewhere anyways with the folio revolution, so it might be a short lived interface anyways. -Andi