From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f200.google.com (mail-io0-f200.google.com [209.85.223.200]) by kanga.kvack.org (Postfix) with ESMTP id 3860C6B0007 for ; Tue, 13 Feb 2018 18:55:14 -0500 (EST) Received: by mail-io0-f200.google.com with SMTP id c1so1139447iob.18 for ; Tue, 13 Feb 2018 15:55:14 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id y9sor6975431itb.58.2018.02.13.15.55.13 for (Google Transport Security); Tue, 13 Feb 2018 15:55:13 -0800 (PST) Date: Tue, 13 Feb 2018 15:55:11 -0800 (PST) From: David Rientjes Subject: Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent In-Reply-To: <20180213154607.f631e2e033f42c32925e3d2d@linux-foundation.org> Message-ID: References: <20180213154607.f631e2e033f42c32925e3d2d@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Jonathan Corbet , Vlastimil Babka , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org On Tue, 13 Feb 2018, Andrew Morton wrote: > > Both kernelcore= and movablecore= can be used to define the amount of > > ZONE_NORMAL and ZONE_MOVABLE on a system, respectively. This requires > > the system memory capacity to be known when specifying the command line, > > however. > > > > This introduces the ability to define both kernelcore= and movablecore= > > as a percentage of total system memory. This is convenient for systems > > software that wants to define the amount of ZONE_MOVABLE, for example, as > > a proportion of a system's memory rather than a hardcoded byte value. > > > > To define the percentage, the final character of the parameter should be > > a '%'. > > Is this fine-grained enough? We've had percentage-based tunables in > the past, and 10 years later when systems are vastly larger, 1% is too > much. > They still have the (current) ability to define the exact amount of bytes down to page sized granularity, whereas 1% would yield 40GB on a 4TB system. I'm not sure that people will want any finer-grained control if defining the proportion of the system for kernelcore. They do have the ability with the existing interface, though, if they want to be that precise. (This is a cop out for not implementing some fractional percentage parser, although that would be possible as a more complete solution.) -- 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