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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pkQDx-00AXes-0w; Thu, 06 Apr 2023 14:04:25 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 94388300194; Thu, 6 Apr 2023 16:04:23 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7CEE5212E36AC; Thu, 6 Apr 2023 16:04:23 +0200 (CEST) Date: Thu, 6 Apr 2023 16:04:23 +0200 From: Peter Zijlstra To: Marcelo Tosatti Cc: Frederic Weisbecker , Yair Podemsky , linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, will@kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, arnd@arndb.de, keescook@chromium.org, paulmck@kernel.org, jpoimboe@kernel.org, samitolvanen@google.com, ardb@kernel.org, juerg.haefliger@canonical.com, rmk+kernel@armlinux.org.uk, geert+renesas@glider.be, tony@atomide.com, linus.walleij@linaro.org, sebastian.reichel@collabora.com, nick.hawkins@hpe.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, vschneid@redhat.com, dhildenb@redhat.com, alougovs@redhat.com, jannh@google.com Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Message-ID: <20230406140423.GA386634@hirez.programming.kicks-ass.net> References: <20230404134224.137038-1-ypodemsk@redhat.com> <20230404134224.137038-4-ypodemsk@redhat.com> <20230405195226.GB365912@hirez.programming.kicks-ass.net> <20230406132928.GM386572@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230406132928.GM386572@hirez.programming.kicks-ass.net> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: jwidzb8mbuawbz783thxxot9nnh6afom X-Rspamd-Queue-Id: 8A05820029 X-HE-Tag: 1680789887-609583 X-HE-Meta: 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 wkGVvlKI UxQNWVd9a6qFyS636NrK/Zjxci7aHm6waMdqNCEmjgzQQcXCes7bYiyxH5f0KIAxbjDrOH7n2yoJ3YcRDfES0rEdwGJ4u5fb81SAnbbMdEoBu6/Tz1wyckCBQv9X6tReh/9xCff00kmanvLQ6SjWs5y79f2dseaHSAloM1PyW9lg3Q4Ue3Z/ZisQf8LHO+wFvAAKrDUVSfKNHZVjuZJMEYUUPhetdTzTSlEa0I3hqZ1uCeA+Jf9ZzR7U3eLyZ20euknnfk+WCDQC6VUCNIK1kUSeWyWJ805XscseU 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 Thu, Apr 06, 2023 at 03:29:28PM +0200, Peter Zijlstra wrote: > On Thu, Apr 06, 2023 at 09:38:50AM -0300, Marcelo Tosatti wrote: > > > > To actually hit this path you're doing something really dodgy. > > > > Apparently khugepaged is using the same infrastructure: > > > > $ grep tlb_remove_table khugepaged.c > > tlb_remove_table_sync_one(); > > tlb_remove_table_sync_one(); > > > > So just enabling khugepaged will hit that path. > > Urgh, WTF.. > > Let me go read that stuff :/ At the very least the one on collapse_and_free_pmd() could easily become a call_rcu() based free. I'm not sure I'm following what collapse_huge_page() does just yet.