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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tH7ob-00000004cmQ-3Ty6; Fri, 29 Nov 2024 20:42:13 +0000 Date: Fri, 29 Nov 2024 20:42:13 +0000 From: Matthew Wilcox To: David Hildenbrand Cc: Lorenzo Stoakes , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] perf: map pages in advance Message-ID: References: <6cab3e8a-dff7-41d1-af22-f18b8f2820dc@lucifer.local> <94dabe57-232b-4a21-b2cf-bcfbda75c881@lucifer.local> <6795cc9a-6230-431f-b089-7909f7bc4f30@redhat.com> <60191c97-dce2-4a92-8b47-c402478ba336@lucifer.local> <9d4ef1a2-11fb-455f-8b37-954215bf25d2@redhat.com> <14895682-a013-419f-bee8-1476540ddedd@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 24F76C0012 X-Stat-Signature: s7ycky48jtwgmt91y3as48j5m5kzhsug X-Rspam-User: X-HE-Tag: 1732912933-730666 X-HE-Meta: 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 XicTPOoq eputjbSLCCxkDiVWaWdLzXwsaZya+VEzG9p+eCTgz301C36JdOHjaQapdLs8rXOt8HdCGue5fwTcnMbgoaGR8Xt+ZA1CV1EhVxrxOivnKMyVueJfeeTNKRWLCnrtg45s6wE8WahMBgSvyuHcId7W7GRMeGP+kpreTuuzI8wKLPP805CNl0H6yMZjdnW3DnBnncsy9IJ/u3NW6U/Bzv2dWsVXcKmnQ0o2RkEQ2pCPFpSlBOe4= 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: On Fri, Nov 29, 2024 at 03:48:33PM +0100, David Hildenbrand wrote: > Too long, but as some of these TODOs stand in the memdesc way, fortunately > other people might be able to give a helping hand at some point ;) ;-) > I'll play with using a page type for some of these "simple" cases and see > how hard it will get. I've deliberately made pagetype incompatible with setting a mapcount ... hugetlb being the exception because we only use entire_mapcount. Anyway, I agree we need something better than what we have here. It needs to be simple for a device driver to allocate memory and map it into userspace. I'm willing to allow perf's ringbuffer to be a bit harder than most because it's trying to do the weird thing of writable-first-page-rest-read-only.