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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-933d325ade8sm489716185a.12.2026.07.30.13.49.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 13:49:26 -0700 (PDT) Date: Thu, 30 Jul 2026 16:49:24 -0400 From: Gregory Price To: Johannes Weiner Cc: Frank van der Linden , Yiannis Nikolakopoulos , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Trond Myklebust , Anna Schumaker , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Brendan Jackman , David Rientjes , Davidlohr Bueso , Fan Ni , Jonathan Cameron , Raghavendra K T , "Rao, Bharata Bhasker" , SeongJae Park , Wei Xu , Xuezheng Chu , Yiannis Nikolakopoulos , dimitrios@palyvos.net, Ryan Roberts , Huan Nguyen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Alirad Malek Subject: Re: [PATCH RFC v2 0/3] Demote to lower tier using non-temporal stores Message-ID: References: <20260730-rfc-nt-demote-v2-0-452dbe3b5073@zptcorp.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Jul 30, 2026 at 02:08:56PM -0400, Johannes Weiner wrote: > On Thu, Jul 30, 2026 at 10:40:32AM -0700, Frank van der Linden wrote: > > On Thu, Jul 30, 2026 at 10:30 AM Gregory Price wrote: > > > arm64 already seems to use stores with NT hints by default. > > > > In general, though, I agree that for ASYNC requests, just always using > > NT seems fine. > > > > Maybe the mode and reason should be folded in to one variable, so > > that, further down the stack, a decision can be made as to what type > > of copy to use? E.g. if the mode is !MIGRATE_ASYNC and the reason is > > MR_DEMOTION, then non-temporal is still a good choice. If the mode is > > MIGRATE_ASYNC, NT is still a good idea. If you wanted to get fancy, > > any mode with folio_test_waiters(folio) == true should not use NT, > > since a task is waiting to use the data, so caching it is better. > > Maybe that's overthinking it. > > Agree. `reason' seems like a much stronger signal. I think this ends up cleaner as well, it would be a nice improvement. ~Gregory