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X-IronPort-AV: E=McAfee;i="6600,9927,10840"; a="379585330" X-IronPort-AV: E=Sophos;i="6.03,166,1694761200"; d="scan'208";a="379585330" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2023 17:37:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10840"; a="740905492" X-IronPort-AV: E=Sophos;i="6.03,166,1694761200"; d="scan'208";a="740905492" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2023 17:37:41 -0700 From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Arjan Van De Ven , Mel Gorman , Vlastimil Babka , David Hildenbrand , Johannes Weiner , Dave Hansen , Michal Hocko , Pavel Tatashin , Matthew Wilcox , Christoph Lameter Subject: Re: [PATCH 00/10] mm: PCP high auto-tuning References: <20230920061856.257597-1-ying.huang@intel.com> <20230920094118.8b8f739125c6aede17c627e0@linux-foundation.org> <87leczwt1o.fsf@yhuang6-desk2.ccr.corp.intel.com> <20230921084617.b1129a46de247e4a6f0098af@linux-foundation.org> Date: Fri, 22 Sep 2023 08:33:52 +0800 In-Reply-To: <20230921084617.b1129a46de247e4a6f0098af@linux-foundation.org> (Andrew Morton's message of "Thu, 21 Sep 2023 08:46:17 -0700") Message-ID: <87h6nnvyfj.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5DFBC20019 X-Stat-Signature: iqw9gdo33ptyzog9aqqot7f3y5ap7eng X-HE-Tag: 1695343065-851749 X-HE-Meta: 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 ziLRUDkn A5k3H9/v0Uu0cWljpoSBHd5mfkQQ4ZAdEGgPkNjQ9K34+mEQJYHactxw/yXyxJrpWCrS+p0nTRtCLxH41pbekVGiTqKpTspsLlr8Krb3LXvW2GAQ78xdT+z8rG7st6tFMpK/8R58cMHa4TByek4vjcAiIVTAUBx8F2gCo2v2hPwOwNgl4co64m0FlMMJ8wPF0OXeVB1QFAGma1eutYi8nEAPlzKqM+emaDjOwpQRuDZ3OSRTMEtokkn6egdE5hIqvSWNpijM9afrziigVzCbqBPojqrdjLC9bC/7vV5tdmLxSPd8aa7/7Lmfy+RdSO/lXITErre38itE30LgarTnBnj6gopmpnLYo9xQj 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: Andrew Morton writes: > On Thu, 21 Sep 2023 21:32:35 +0800 "Huang, Ying" wrote: > >> > : It's possible that PCP high auto-tuning doesn't work well for some >> > : workloads. So, when PCP high is tuned by hand via the sysctl knob, >> > : the auto-tuning will be disabled. The PCP high set by hand will be >> > : used instead. >> > >> > Is it a bit hacky to disable autotuning when the user alters >> > pcp-high? Would it be cleaner to have a separate on/off knob for >> > autotuning? >> >> This was suggested by Mel Gormon, >> >> https://lore.kernel.org/linux-mm/20230714140710.5xbesq6xguhcbyvi@techsingularity.net/ >> >> " >> I'm not opposed to having an adaptive pcp->high in concept. I think it would >> be best to disable adaptive tuning if percpu_pagelist_high_fraction is set >> though. I expect that users of that tunable are rare and that if it *is* >> used that there is a very good reason for it. >> " >> >> Do you think that this is reasonable? > > I suppose so, if it's documented! > > Documentation/admin-guide/sysctl/vm.rst describes > percpu_pagelist_high_fraction. Sure. Will add document about auto-tuning behavior in the above document. -- Best Regards, Huang, Ying