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X-CSE-ConnectionGUID: 0iiYDLrQQeqWGPjcT0waxA== X-CSE-MsgGUID: 4PnP6VfjQnCLlbAN/N5N3Q== X-IronPort-AV: E=McAfee;i="6700,10204,11168"; a="26043705" X-IronPort-AV: E=Sophos;i="6.10,158,1719903600"; d="scan'208";a="26043705" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Aug 2024 00:49:36 -0700 X-CSE-ConnectionGUID: asTOiE4QTIyNsuC0IRWF6w== X-CSE-MsgGUID: FdIuexS/S0is/hp7S2MxtA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,158,1719903600"; d="scan'208";a="60281715" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Aug 2024 00:49:33 -0700 From: "Huang, Ying" To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, david@redhat.com, nphamcs@gmail.com, nehagholkar@meta.com, abhishekd@meta.com, Johannes Weiner Subject: Re: [PATCH 0/3] mm,TPP: Enable promotion of unmapped pagecache In-Reply-To: <20240803094715.23900-1-gourry@gourry.net> (Gregory Price's message of "Sat, 3 Aug 2024 05:47:12 -0400") References: <20240803094715.23900-1-gourry@gourry.net> Date: Mon, 19 Aug 2024 15:46:00 +0800 Message-ID: <875xrxhs5j.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Stat-Signature: 5sk8jfyhgbyws4e6zm5tkpe46sgeqaqq X-Rspamd-Queue-Id: 0BDCD180005 X-Rspamd-Server: rspam11 X-HE-Tag: 1724053790-462751 X-HE-Meta: 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 3IwHgHbF LCkZFDAqpLUOwoMCngoayF+/akSbfkDeo6fo95mS3V778wv+mdwuCUkMZb3yl8KM1mkzEYWHi2O+b93yExuk+6wHhykIe53WHsRlS9I51q8Yc00B6f+BhkClzgeaA/vdqX/w7eh6RPcsmfHw7nwC9wO+6Nkm+Szt//3v/bJRd/nYZ70WxztXFj4T/oUiin+6WJHus7wE8iCgRQK2YqTdYIl0SzrHrt7vjr5Hm 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: Gregory Price writes: > Unmapped pagecache pages can be demoted to low-tier memory, but > they can only be promoted if a process maps the pages into the > memory space (so that NUMA hint faults can be caught). This can > cause significant performance degradation as the pagecache ages > and unmapped, cached files are accessed. > > This patch series enables the pagecache to request a promotion of > a folio when it is accessed via the pagecache. > > We add a new `numa_hint_page_cache` counter in vmstat to capture > information on when these migrations occur. It appears that you will promote page cache page on the second access. Do you have some better way to identify hot pages from the not-so-hot pages? How to balance between unmapped and mapped pages? We have hot page selection for hot pages. [snip] -- Best Regards, Huang, Ying