From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 28 Jan 2016 20:55:34 -0500 From: Johannes Weiner To: Daniel Walker Cc: Alexander Viro , Michal Hocko , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Khalid Mughal (khalidm)" , "xe-kernel@external.cisco.com" , Rik van Riel Subject: Re: computing drop-able caches Message-ID: <20160129015534.GA6401@cmpxchg.org> References: <56AAA77D.7090000@cisco.com> <20160128235815.GA5953@cmpxchg.org> <56AABA79.3030103@cisco.com> <56AAC085.9060509@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56AAC085.9060509@cisco.com> Sender: owner-linux-mm@kvack.org List-ID: On Thu, Jan 28, 2016 at 05:29:41PM -0800, Daniel Walker wrote: > On 01/28/2016 05:03 PM, Daniel Walker wrote: > [regarding MemAvaiable] > > This new metric purportedly helps usrespace assess available memory. But, > its again based on heuristic, it takes 1/2 of page cache as reclaimable.. No, it takes the smaller value of cache/2 and the low watermark, which is a fraction of memory. Actually, that does look a little weird. Rik? We don't age cache without memory pressure, you don't know how much is used until you start taking some away. Heuristics is all we can offer. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755476AbcA2B4C (ORCPT ); Thu, 28 Jan 2016 20:56:02 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:55456 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751462AbcA2Bz7 (ORCPT ); Thu, 28 Jan 2016 20:55:59 -0500 Date: Thu, 28 Jan 2016 20:55:34 -0500 From: Johannes Weiner To: Daniel Walker Cc: Alexander Viro , Michal Hocko , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Khalid Mughal (khalidm)" , "xe-kernel@external.cisco.com" , Rik van Riel Subject: Re: computing drop-able caches Message-ID: <20160129015534.GA6401@cmpxchg.org> References: <56AAA77D.7090000@cisco.com> <20160128235815.GA5953@cmpxchg.org> <56AABA79.3030103@cisco.com> <56AAC085.9060509@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56AAC085.9060509@cisco.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2016 at 05:29:41PM -0800, Daniel Walker wrote: > On 01/28/2016 05:03 PM, Daniel Walker wrote: > [regarding MemAvaiable] > > This new metric purportedly helps usrespace assess available memory. But, > its again based on heuristic, it takes 1/2 of page cache as reclaimable.. No, it takes the smaller value of cache/2 and the low watermark, which is a fraction of memory. Actually, that does look a little weird. Rik? We don't age cache without memory pressure, you don't know how much is used until you start taking some away. Heuristics is all we can offer.