From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f179.google.com (mail-ig0-f179.google.com [209.85.213.179]) by kanga.kvack.org (Postfix) with ESMTP id 7FB5C6B0009 for ; Tue, 16 Feb 2016 00:38:32 -0500 (EST) Received: by mail-ig0-f179.google.com with SMTP id g6so23736928igt.1 for ; Mon, 15 Feb 2016 21:38:32 -0800 (PST) Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net. [150.101.137.141]) by mx.google.com with ESMTP id n9si32301504iga.37.2016.02.15.21.38.30 for ; Mon, 15 Feb 2016 21:38:32 -0800 (PST) Date: Tue, 16 Feb 2016 16:38:28 +1100 From: Dave Chinner Subject: Re: [PATCH] kernel: fs: drop_caches: add dds drop_caches_count Message-ID: <20160216053827.GX19486@dastard> References: <1455308080-27238-1-git-send-email-danielwa@cisco.com> <20160214211856.GT19486@dastard> <56C216CA.7000703@cisco.com> <20160215230511.GU19486@dastard> <56C264BF.3090100@cisco.com> <20160216004531.GA28260@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: "Nag Avadhanam (nag)" Cc: Theodore Ts'o , "Daniel Walker (danielwa)" , Alexander Viro , "Khalid Mughal (khalidm)" , "xe-kernel@external.cisco.com" , "dave.hansen@intel.com" , "hannes@cmpxchg.org" , "riel@redhat.com" , Jonathan Corbet , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" On Tue, Feb 16, 2016 at 02:58:04AM +0000, Nag Avadhanam (nag) wrote: > Its the calculation of the # of bytes of non-reclaimable file system cache > pages that has been troubling us. We do not want to count inactive file > pages (of programs/binaries) that were once mapped by any process in the > system as reclaimable because that might lead to thrashing under memory > pressure (we want to alert admins before system starts dropping text > pages). The code presented does not match your requirements. It only counts pages that are currently mapped into ptes. hence it will tell you that once-used and now unmapped binary pages are reclaimable, and drop caches will reclaim them. hence they'll need to be fetched from disk again if they are faulted in again after a drop_caches run. Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org