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X-CSE-ConnectionGUID: vZYl20q6SGOko0wYbkePiQ== X-CSE-MsgGUID: yhfzBrd/QkG7F2qwygPOrg== X-IronPort-AV: E=McAfee;i="6800,10657,11623"; a="69864643" X-IronPort-AV: E=Sophos;i="6.20,223,1758610800"; d="scan'208";a="69864643" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2025 09:05:37 -0800 X-CSE-ConnectionGUID: LNeMYZhaSq6aHIS5tAfYCg== X-CSE-MsgGUID: b4i3KSt9S1mZxtRZe0tx4A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.20,223,1758610800"; d="scan'208";a="196545997" Received: from egrumbac-mobl6.ger.corp.intel.com (HELO localhost) ([10.245.244.5]) by ORVIESA003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2025 09:05:35 -0800 Date: Mon, 24 Nov 2025 19:05:32 +0200 From: Andy Shevchenko To: Andrew Morton Cc: Ilias Stamatis , linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, nadav.amit@gmail.com, huang.ying.caritas@gmail.com, bhe@redhat.com, nh-open-source@amazon.com Subject: Re: [PATCH] Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()" Message-ID: References: <20251124165349.3377826-1-ilstam@amazon.com> <20251124085816.07dbf5a4ec6235b2943840a0@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251124085816.07dbf5a4ec6235b2943840a0@linux-foundation.org> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo X-Rspamd-Queue-Id: 8250E14000F X-Stat-Signature: ofk7ihknz1p56dc1qsowyw5ber1wt49t X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1764003939-64862 X-HE-Meta: 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 PUd+v6v8 a4TqckSNlB0Vl6fIck2nuBlFc4kjGE0gAgAwq1Qa+TdCWEHtbKizsivdNhEUqIWa6FMYqZtxjBibmKvm8cyHLtGdNd0g02zk5qmXjBu21MoO47npO7AQzMCtGDY6EsggtOUMYIQuebPztM+biOYN7mICZ2RQvERyE/2U0U+Zu/uGntHSpO8VIKSYGIrxmiHYi/DtX/uYtSvMIZK7qaTm2KeKGlm8St0BHGa8mYMQPHJWy79fzmi89iEOJcT40xNoBCIHgQstJLgoVUV/7oEQrTZAQh1DEpgBfX7tfScWN3QJ+mOTKolgg+h5lqKJkg7ONOxKDoL84Gb294znLoTUE/JDmkrnPboDg8f3o1MjEU+0mFQryyoN7hlk4qgyK1+q3bcRU 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, Nov 24, 2025 at 08:58:16AM -0800, Andrew Morton wrote: > On Mon, 24 Nov 2025 16:53:49 +0000 Ilias Stamatis wrote: > > > Commit 97523a4edb7b ("kernel/resource: remove first_lvl / siblings_only > > logic") removed an optimization introduced by commit 756398750e11 > > ("resource: avoid unnecessary lookups in find_next_iomem_res()"). That > > was not called out in the message of the first commit explicitly so it's > > not entirely clear whether removing the optimization happened > > inadvertently or not. > > > > As the original commit message of the optimization explains there is no > > point considering the children of a subtree in find_next_iomem_res() if > > the top level range does not match. Reinstating the optimization results > > in significant performance improvements in systems with very large iomem > > maps when mmaping /dev/mem. > > It would be great if we could quantify "significant performance > improvements"? +1. It also would be good to know which exact function(s) is a bottleneck. The mentioned change updated a handful of them. -- With Best Regards, Andy Shevchenko