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[84.229.251.248]) by smtp.gmail.com with ESMTPSA id k10-20020a5d6e8a000000b002d1daafea30sm13889142wrz.34.2023.03.22.07.11.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 07:11:46 -0700 (PDT) Message-ID: Subject: Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs From: ypodemsk@redhat.com To: Peter Zijlstra Cc: will@kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, npiggin@gmail.com, arnd@arndb.de, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mtosatti@redhat.com, ppandit@redhat.com, alougovs@redhat.com, David Hildenbrand Date: Wed, 22 Mar 2023 16:11:44 +0200 In-Reply-To: <20230320084902.GE2194297@hirez.programming.kicks-ass.net> References: <20230312080945.14171-1-ypodemsk@redhat.com> <20230320084902.GE2194297@hirez.programming.kicks-ass.net> X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) Mime-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: D1CF44000F X-Rspamd-Server: rspam01 X-Stat-Signature: re34si9hycnuzdztwefp3nzkjnz8omoj X-HE-Tag: 1679494310-871040 X-HE-Meta: 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 glFEY5iM 9bCINAtkZPsBv8WPyund7i7IbKVTkr6ufdgo3qdr1geWe18h0tbmYY7aE+yDAZ+zFybQ2W6uQ5cRg7naTJgYgobi1T7H79boZKyHD80t9yXSXthQA9B+ZRuA0frDrf8mdLBh+1EdxgNE0tbaSl+kOpFCYPV0d9CVYkYxK/zQc0gWW6WaFcGpnZMOKJi5C/elSVisLIYpZ3vU79FohaoSgGIZw6MI4muTgTHGsbzmvRsqDBqwM1uCv3leduBa7GmcVDssAchHmc5bfBgSUEn4VRK5YuFQH5In7aqCk5vVeVSSS32KK8bwwaOFEPLfX/iWPj5ifRrL+94Rncasgl3svZaNJTx8CrX1bWvifZMdG8Ul3Hc8bmZbltHK6bMwcW94/5pdseaJv837xOG6c4Mbuei8ltbwgqJRuIvwF+v/BdpZaaA9lZCI1Ce2shRB75ZPlQA012vWT5SvZk8Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 2023-03-20 at 09:49 +0100, Peter Zijlstra wrote: > On Sun, Mar 12, 2023 at 10:09:45AM +0200, Yair Podemsky wrote: > > Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs > > indiscriminately, this causes unnecessary work and delays notable > > in > > real-time use-cases and isolated cpus, this patch will limit this > > IPI to > > only be sent to cpus referencing the effected mm and are currently > > in > > kernel space. > > Did you validate that all architectures for which this is relevant > actually set bits in mm_cpumask() ? > Hi Peter, Thank you for bringing this to my attention. I reviewed the architectures using the MMU_GATHER_RCU_TABLE_FREE: arm, powerpc, s390, sparc and x86 set the bit when switching process in. for arm64 removed set/clear bit in 38d96287504a ("arm64: mm: kill mm_cpumask usage") The reason given was that mm_cpumask was not used. Given that we now have a use for it, I will add a patch to revert. Thanks Yair