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X-CSE-ConnectionGUID: bq5QX7D6Q26fmkKYHWUu7Q== X-CSE-MsgGUID: 7UlX88nkQSmbGeOjQvGmhw== X-IronPort-AV: E=McAfee;i="6800,10657,11692"; a="82874867" X-IronPort-AV: E=Sophos;i="6.21,274,1763452800"; d="scan'208";a="82874867" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Feb 2026 07:09:18 -0800 X-CSE-ConnectionGUID: MR7SxKoTQQOkJJrYuLxBvw== X-CSE-MsgGUID: 2dRbd5IjRTC6xZWZm68x7w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,274,1763452800"; d="scan'208";a="210470361" Received: from tfalcon-desk.amr.corp.intel.com (HELO [10.125.111.86]) ([10.125.111.86]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Feb 2026 07:09:17 -0800 Message-ID: <64f3a75a-30ff-4bee-833c-be5dba05f72b@intel.com> Date: Thu, 5 Feb 2026 07:09:15 -0800 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/3] targeted TLB sync IPIs for lockless page table To: Lance Yang , "David Hildenbrand (Arm)" , Peter Zijlstra Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, aneesh.kumar@kernel.org, arnd@arndb.de, baohua@kernel.org, baolin.wang@linux.alibaba.com, boris.ostrovsky@oracle.com, bp@alien8.de, dave.hansen@linux.intel.com, dev.jain@arm.com, hpa@zytor.com, hughd@google.com, ioworker0@gmail.com, jannh@google.com, jgross@suse.com, kvm@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, npache@redhat.com, npiggin@gmail.com, pbonzini@redhat.com, riel@surriel.com, ryan.roberts@arm.com, seanjc@google.com, shy828301@gmail.com, tglx@linutronix.de, virtualization@lists.linux.dev, will@kernel.org, x86@kernel.org, ypodemsk@redhat.com, ziy@nvidia.com References: <20260202095414.GE2995752@noisy.programming.kicks-ass.net> <20260202110329.74397-1-lance.yang@linux.dev> <20260202125030.GB1395266@noisy.programming.kicks-ass.net> <4700e7ba-8456-4a93-9e28-7e5a3ca2a1be@linux.dev> <20260202133713.GF1395266@noisy.programming.kicks-ass.net> <540adec9-c483-460a-a682-f2076cf015c2@linux.dev> <20260202150957.GD1282955@noisy.programming.kicks-ass.net> <06d48a52-e4ec-47cd-b3fb-0fccd4dc49f4@kernel.org> <3026ad8d-92ad-4683-8c3e-733d4070d033@linux.dev> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/5/26 07:01, Lance Yang wrote: > So for now, neither approach looks good: tracking on the read side adss > cost to GUP-fast, and syncing on the write side e.g. synchronize_rcu() > is too slow on large systems. Which of the writers truly *need* synchronize_rcu()? What are they doing with the memory that they can't move forward unless it's quiescent *now*?