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X-IronPort-AV: E=McAfee;i="6600,9927,10978"; a="5194096" X-IronPort-AV: E=Sophos;i="6.05,256,1701158400"; d="scan'208";a="5194096" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Feb 2024 01:56:04 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,256,1701158400"; d="scan'208";a="6535901" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.54.38.190]) by orviesa005.jf.intel.com with ESMTP; 09 Feb 2024 01:56:03 -0800 Received: by tassilo.localdomain (Postfix, from userid 1000) id 9D2E8301B21; Fri, 9 Feb 2024 01:56:03 -0800 (PST) From: Andi Kleen To: Chunsheng Luo Cc: gregkh@linuxfoundation.org, rafael@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] meminfo: provide estimated per-node's available memory In-Reply-To: <20240204083414.107799-1-luochunsheng@ustc.edu> (Chunsheng Luo's message of "Sun, 4 Feb 2024 03:34:14 -0500") References: <20240204083414.107799-1-luochunsheng@ustc.edu> Date: Fri, 09 Feb 2024 01:56:03 -0800 Message-ID: <87fry2t0zw.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 60BE8C0019 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: r4ofk49u1jeirekscfoktr6y3jxf3odh X-HE-Tag: 1707472566-204835 X-HE-Meta: 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 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: Chunsheng Luo writes: > + available = sum_zone_node_page_state(nid, NR_FREE_PAGES) - pgdat->totalreserve_pages; > + > + /* > + * Not all the page cache can be freed, otherwise the system will > + * start swapping or thrashing. Assume at least half of the page > + * cache, or the low watermark worth of cache, needs to stay. > + */ > + pagecache = node_page_state(pgdat, NR_ACTIVE_FILE) + > + node_page_state(pgdat, NR_INACTIVE_FILE); > + pagecache -= min(pagecache / 2, wmark_low); The magic number 2 should be a define (or maybe even a tunable). Similar below. It seems quite arbitrary, but I don't have a better solution either. Maybe could handle dirty differently, but nothing stands out here > + node_page_state(pgdat, NR_KERNEL_MISC_RECLAIMABLE); > + reclaimable -= min(reclaimable / 2, wmark_low); > + available += reclaimable; > + > + if (available < 0) > + available = 0; That would be a bug? Perhaps add a WARN_ON With those changes: Reviewed-by: Andi Kleen -Andi