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X-CSE-ConnectionGUID: +OdYyag0TdaWvJb55CoNOg== X-CSE-MsgGUID: 7Q3iBOKuRva20HAIXyIllw== X-IronPort-AV: E=McAfee;i="6600,9927,11088"; a="24173148" X-IronPort-AV: E=Sophos;i="6.08,201,1712646000"; d="scan'208";a="24173148" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2024 06:50:49 -0700 X-CSE-ConnectionGUID: z41EsDgCR8uiPNQaCCb33g== X-CSE-MsgGUID: e0kVWSzwQe+g0OS56Halmw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,201,1712646000"; d="scan'208";a="66676010" Received: from kinlongk-desk.amr.corp.intel.com (HELO [10.125.111.178]) ([10.125.111.178]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2024 06:50:49 -0700 Message-ID: <2a0f8cc9-a061-45cd-81df-b65d4b454b77@intel.com> Date: Thu, 30 May 2024 06:50:48 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 00/12] LUF(Lazy Unmap Flush) reducing tlb numbers over 90% To: Byungchul Park , "Huang, Ying" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org, vernhao@tencent.com, mgorman@techsingularity.net, hughd@google.com, willy@infradead.org, david@redhat.com, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, rjgolo@gmail.com References: <982317c0-7faa-45f0-82a1-29978c3c9f4d@intel.com> <20240527015732.GA61604@system.software.com> <8734q46jc8.fsf@yhuang6-desk2.ccr.corp.intel.com> <44e4f2fd-e76e-445d-b618-17a6ec692812@intel.com> <20240529050046.GB20307@system.software.com> <961f9533-1e0c-416c-b6b0-d46b97127de2@intel.com> <20240530005026.GA47476@system.software.com> <87a5k814tq.fsf@yhuang6-desk2.ccr.corp.intel.com> <20240530071847.GA15344@system.software.com> <871q5j1zdf.fsf@yhuang6-desk2.ccr.corp.intel.com> <20240530084120.GA12940@system.software.com> 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 5/30/24 01:41, Byungchul Park wrote: > LUF should not optimize tlb flushes for mappings that users explicitly > change e.g. through mmap() and munmap(). We are thoroughly going around in circles at this point. I'm not quite sure what to do. Ying and I see a problem that we've tried to explain a couple of times. We've tried to show the connection between a LUF-elided TLB flush and how that could affect a later munmap() or mmap(MAP_FIXED). But these responses seem to keep going back to the fact that LUF doesn't directly affect munmap(), which is true, but quite irrelevant to the problem being described. So we're at an impasse. Byungchul, perhaps you should spin another series and maybe Ying and I have to write up a test case to show the bug that we see. Or perhaps someone else can jump into the thread and bridge the communication gap.