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d=linux-foundation.org; s=korg; t=1695311178; bh=XbJgWS2b4Zs6ittxozTQbmeIioM0YEqG8HDmDMXPv/U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=EmOPQtjpihFmSGI9lHQLn9ZbTdoa0pDV27Y6p+DgCqQoWSEhawxxqTaWPvbBMcyJx 8UpdnxNbLOTXxxk/BLuxsf5jEk3FvH8kQjP6E9KJ5eR44XXCyBAEdKjkqVSBXXwJJL 9jM2G7bH41H4C/HV/mVrPcN1LEbU5kxxFGjheoTQ= Date: Thu, 21 Sep 2023 08:46:17 -0700 From: Andrew Morton To: "Huang, Ying" 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 Message-Id: <20230921084617.b1129a46de247e4a6f0098af@linux-foundation.org> In-Reply-To: <87leczwt1o.fsf@yhuang6-desk2.ccr.corp.intel.com> References: <20230920061856.257597-1-ying.huang@intel.com> <20230920094118.8b8f739125c6aede17c627e0@linux-foundation.org> <87leczwt1o.fsf@yhuang6-desk2.ccr.corp.intel.com> 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: rspam09 X-Rspamd-Queue-Id: 4961B40013 X-Stat-Signature: sp31tjjp9h9s38y6gr5qs4bm1qgmp5uw X-Rspam-User: X-HE-Tag: 1695311183-31670 X-HE-Meta: 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 /4Oo7blr +9S4n0JHD8o6WLepSacu/1sb51Y1KXwyOBgqazO6rwKSDkjHEZF7ZvLuUTtUPOOYMjr+8APpx6IOCk1W4HdZAtgOFkW3zLjPVm0v2emteRB85Ztb+dzObPe3/T0p61ldht9zzUNcj6z3w2m4gVLOFRn2KUaIhlsxF/2c2o9g/UcIpVkn5atTAy0woQ8iAL7WawSm7zTufAiuDBvrBwTTiktpZC+wqFQtjjO2yDjPsNMsi7PVJTLOIRlHfeHKpZqFk30Ssoag91WSTl77gf4Lnxt/IC9mpaBeFTTUqVYoNhuvj29odlmKr8YbCGGCvjXoNc3LI+bbBayyy6AtzolNLrb31ZC/Glyl+eEiBd5lgSdrNFiXElutHFkdXY0heDBfRACPtMU2aNKrmqrenFq2EVW4aUyk/BQYxel86LWx7n5LgVZvr2U4HU23BM52u6AlNnuxQH5SUCaHY+cAygldY548A/Q== 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: 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.