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X-IronPort-AV: E=McAfee;i="6600,9927,10840"; a="361022403" X-IronPort-AV: E=Sophos;i="6.03,167,1694761200"; d="scan'208";a="361022403" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2023 00:58:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10840"; a="817692142" X-IronPort-AV: E=Sophos;i="6.03,167,1694761200"; d="scan'208";a="817692142" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2023 00:58:48 -0700 From: "Huang, Ying" To: Sudeep Holla Cc: , , Arjan Van De Ven , "Andrew Morton" , Mel Gorman , Vlastimil Babka , "David Hildenbrand" , Johannes Weiner , "Dave Hansen" , Michal Hocko , "Pavel Tatashin" , Matthew Wilcox , Christoph Lameter Subject: Re: [PATCH 02/10] cacheinfo: calculate per-CPU data cache size References: <20230920061856.257597-1-ying.huang@intel.com> <20230920061856.257597-3-ying.huang@intel.com> <20230920092402.pvqju4knnqkzqfiq@bogus> Date: Fri, 22 Sep 2023 15:56:41 +0800 In-Reply-To: <20230920092402.pvqju4knnqkzqfiq@bogus> (Sudeep Holla's message of "Wed, 20 Sep 2023 10:24:02 +0100") Message-ID: <87cyyawshy.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: 4DBC540020 X-Stat-Signature: ngfmmw8t1hdedakctw848p1znfi76z7s X-HE-Tag: 1695369533-197461 X-HE-Meta: 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 soAhBD6K ig2JppOQrwEWfg85yaeM9D5dhW/VXkviUIttcYMEyjOzLS/e6t+I3PmOOVKLzt1qIjLLmkeuJzFveEiVEQeJ67flbYiaXHmoUjBSK6vFgB67gmCVlqTQT8/WrjvGdXE52InMz2GT5mk46yC+ieB9H5MdU+aZjczwAfFJNgdun+wNZmfuwtgZy9vqaYDcbpGzxf+rA4pZU3mn9d1FxCQmHgbEp6Cxj8xomWb0B81E/HvsPLkaFztrp99Z/Yes7mEiu7x/4QJlbOT66Km/FCIKSprTV5bzsA/2nKpE/ 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: Sudeep Holla writes: > On Wed, Sep 20, 2023 at 02:18:48PM +0800, Huang Ying wrote: >> Per-CPU data cache size is useful information. For example, it can be >> used to determine per-CPU cache size. So, in this patch, the data >> cache size for each CPU is calculated via data_cache_size / >> shared_cpu_weight. >> >> A brute-force algorithm to iterate all online CPUs is used to avoid >> to allocate an extra cpumask, especially in offline callback. >> > > You have not mentioned who will use this information ? Looking at the > change, it is not exposed to the user-space. Also I see this is actually > part of the series [1]. Is this info used in any of those patches ? Can you > point me to the same ? Yes. It is used by [PATCH 03/10] of the series. If the per-CPU data cache size is large enough, we will cache more pages in the per-CPU pageset to reduce the zone lock contention. > Not all architecture use cacheinfo yet. How will the mm changes affect those > platforms ? If cacheinfo isn't available, we will fallback to the original behavior. That is, we will drain per-CPU pageset more often (that is, cache less to improve cache-hot pages sharing between CPUs). > -- > Regards, > Sudeep > > [1] https://lore.kernel.org/all/20230920061856.257597-1-ying.huang@intel.com/ -- Best Regards, Huang, Ying