Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932200Ab2JJO3A (ORCPT ); Wed, 10 Oct 2012 10:29:00 -0400 Received: from mail-qc0-f174.google.com ([209.85.216.174]:50585 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756464Ab2JJO25 (ORCPT ); Wed, 10 Oct 2012 10:28:57 -0400 Date: Wed, 10 Oct 2012 10:17:08 -0400 From: Konrad Rzeszutek Wilk To: Yinghai Lu Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jacob Shin , Tejun Heo , Stefano Stabellini , linux-kernel@vger.kernel.org Subject: Re: [PATCH 03/10] x86, mm: get early page table from BRK Message-ID: <20121010141707.GH4005@phenom.dumpdata.com> References: <1349757558-10856-1-git-send-email-yinghai@kernel.org> <1349757558-10856-4-git-send-email-yinghai@kernel.org> <20121009160133.GF7639@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 27 On Tue, Oct 09, 2012 at 06:03:33PM -0700, Yinghai Lu wrote: > On Tue, Oct 9, 2012 at 9:01 AM, Konrad Rzeszutek Wilk wrote: > >> +RESERVE_BRK(early_pgt_alloc, 16384); > > > > How did you come up with 16KB being the right size? What is this > > based on? Can you provide a comment explaining why 16KB is the > > right value on 32-bit and 64-bit machines? > > good point, i add one line comment to the revised patch. > > +/* need 3 4k for initial PMD_SIZE, 4k for 0-ISA_END_ADDRESS */ Can you explain the math please? It sounds like this is based on the assumption that this you are using huge pages. But what if you are not? What if you can only do 4KB pages? > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/