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bh=2AcWw4U7YmKhyTQRefWWqoVh+t5hGac5B/I1GEORDcs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Zzel3ow2bRiSIP0uPoMOj3Tjki4KkCXh7YbB8eL/QTEZhbndhov4+1S/2mYlsbS8m luqNLI1F6hwOAv/xgkt6VRZPUwd6GyEqbGjmuKHjT4XMYEbuslKmQf97b7aRjKFnj/ 0NuMEF8wpIB1dc0gJBGzG/pt7pQTQCdhPN4/gpQGPPmjiyxioUWKzcA0TvWl6g+LLd mQUJV0M94I5y4IfFJU+1IOwxk/5KkeUREzRCdqf/63Z4+WmQw/lEQQOeO0O1Y305Q2 tJuzPAzLuXsby6sl5MvGE9aD2TDimW1sXGN/IuwVeQMMTfDBtv+4Z+myCoacgasg5a UdxITN47UaYaQ== Date: Fri, 24 Mar 2023 15:13:00 +0000 From: Will Deacon To: ypodemsk@redhat.com Cc: Peter Zijlstra , 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 Subject: Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs Message-ID: <20230324151259.GC27199@willie-the-truck> References: <20230312080945.14171-1-ypodemsk@redhat.com> <20230320084902.GE2194297@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: AC0AB10001E X-Stat-Signature: iymx51g7ayo1skhcmqjwbu8iou9k3prn X-HE-Tag: 1679670789-767453 X-HE-Meta: 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 lv6imE/l tJihy0fET7R6tleajgri+lu4gGKxvVVu0xxJpPk+kJmt+cHOwK1rCizorWdj6TTY3ThPDz1DjOjye4tD32sisE8DoYfZ9sx35FS2f5GpeVsNWsFxCRzcRz0O4cjpaEzUq85plcLFKJ+3ab0vwPqqZtkdwgkl1lL2DqDkdeVBsfGqUeKzaNY1rELpqu57I6NFT/SmZ9hM+Moq5BsemC799mYtMnkzmvi4ES50XXFDyYzUFrc8IAae1TWjuja/8Tf4W54BUwVXBDEXRtPqC9PX5irh+YI0lVmIvVjLy+nn3php9D1RcRaoQzMXL5nKVBPVCOfY1R+s425ZDm/hnYEjnrRAKrh4QBWhdFLiblMTPlWc8du1pfB8Q2fqNyA== 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 Wed, Mar 22, 2023 at 04:11:44PM +0200, ypodemsk@redhat.com wrote: > 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. Maintaining the mask is also not free, so I'm not keen on adding it back unless there's a net win. Will