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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e43baacb5dsm43149896d6.88.2025.02.09.21.36.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 09 Feb 2025 21:36:19 -0800 (PST) Date: Mon, 10 Feb 2025 00:36:16 -0500 From: Gregory Price To: Andrew Morton Cc: Joshua Hahn , hyeonggon.yoo@sk.com, ying.huang@linux.alibaba.com, honggyu.kim@sk.com, rafael@kernel.org, lenb@kernel.org, gregkh@linuxfoundation.org, rakie.kim@sk.com, dan.j.williams@intel.com, Jonathan.Cameron@huawei.com, dave.jiang@intel.com, horen.chuang@linux.dev, hannes@cmpxchg.org, linux-kernel@vger.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: Re: [PATCH v5] mm/mempolicy: Weighted Interleave Auto-tuning Message-ID: References: <20250207201335.2105488-1-joshua.hahnjy@gmail.com> <20250207182009.7fc099c3074ad00338f25e0a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250207182009.7fc099c3074ad00338f25e0a@linux-foundation.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0FDB4A0003 X-Stat-Signature: xeno7h3kakeyty3c9nhj53qoqffouz61 X-HE-Tag: 1739165780-188256 X-HE-Meta: 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 Abt5jcJX 5lnKXYfTQwjSpv02avgUt1gyU/08lawjI5RiQUDMgk0jXExCvzaQ3B7X/E5lrRolzPiQUD5t3BEiw4qqzI3Kdq2bksp+cd6hJA82Tg50sNZ/gBMazhPOc0NV37T618yOa30kClGBC8/9Ebdxgx0o+w40/rf+KnLrQMf6Qwjq331GGdIZR0kp+qCr3KC9r4pmBWIkNs3C6KFVbTD//rvcgRJJ1+3z7LasPILMhgWKt8N0UMvUuLMx8tYWd4NYTxdSQQCmA+3dgPc6KeaOnR0oOgnIFMjtHBsRrIwxu65Ik5bNBszYo09zM8byfxu0LMht2cnjhcaFrfgzLsStHk/BLtldixD4TuDE/o05bjr2Mxtb8ZZrzpi4phQX7Wy2ORSji7IcpMDqrE3ItJqQfQm8fwbJ+BusjGuKYMn4S9J69BgRM6g4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.005333, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 07, 2025 at 06:20:09PM -0800, Andrew Morton wrote: > On Fri, 7 Feb 2025 12:13:35 -0800 Joshua Hahn wrote: > > Leading to... how do we know that this patch makes the kernel better? Just focusing on this question: The default behavior of weighted interleave without this patch is equivalent to normal interleave. This provides a differentiation out-of-the box, and that's just a better experience. We may find the default values / calculations need tweaking in the future, but this gives us a good starting point. Anecdotally, I've seen an "optimal" distribution of 10:1 based on the numbers run sub-optimally compared to 7:1 or 13:1 (but better than default mempol). So there will always be a "try it and see" component to this. (Not to mention hardware/firmware lies regularly, and their reported performance numbers rarely if ever match their tested numbers - so *at best* this can be considered a best-effort feature) ~Gregory