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b=JzCRggp4W0TtGGt058AdSYkUxteplcjAuD7YWfnxvkIg/OVvXLnIglxjfORx02ga+ 163pl7nAg3VZg495M6pMhKMVoSr3S2pQYAiKfZJQVaco+GUNrC3Kw5owAIxMDrpbXQ jHmgX6gRd9zCVHRtH8JCA1dLa+CJeFCAj5VryZCM= Date: Mon, 10 Feb 2025 16:39:41 -0800 From: Andrew Morton To: Gregory Price 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: <20250210163941.15da1e935ed47aacf810fdd0@linux-foundation.org> In-Reply-To: References: <20250207201335.2105488-1-joshua.hahnjy@gmail.com> <20250207182009.7fc099c3074ad00338f25e0a@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CC954140005 X-Stat-Signature: 1yfjtjehbr3qpwz85p1nf88qkzh1t17k X-Rspam-User: X-HE-Tag: 1739234383-717496 X-HE-Meta: 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 23MO4zkO W6eI9HKqvgSB0ceMaaJw/R5W0I0iNZ1NUuIo1d82TQ/qlHrrGd/vhf53Ro//jTZQHSUfWxBGlrwsBcgQAKafFdqN+NdQDGGwZf0supV8YBtHwhYdsulmZSkxFb/ZeSBZnm4nRhcx8oBkU7EqxghMe5sdtfb9arQMe5ucDC1/pViLnQyky8pVLAikYU4s//gF+SM3xUX/wuC2k609szloFR0P0wrXA8S7UAWhFHPK2XamB2rVeg/WM8Pc59sGovm/OZ0wzYc300YwAU+o2Y23IK5ktjqgjx5nlA1mEE16blWDBhp8+SIiEevIglqrn2GFeFterOYvTbWhLRK7WJIrh7w+LZXidhCYGp1RcSf1Upa2EzD7tEcimPoArviu8QDKqPaOfznHWjEFrL4vdvo1aqBoVfQ== 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: List-Subscribe: List-Unsubscribe: On Mon, 10 Feb 2025 00:36:16 -0500 Gregory Price wrote: > 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). How was this optimality measured/observed? > 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)