Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751562AbaLEMbc (ORCPT ); Fri, 5 Dec 2014 07:31:32 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:45231 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750823AbaLEMbb (ORCPT ); Fri, 5 Dec 2014 07:31:31 -0500 Date: Fri, 5 Dec 2014 12:31:17 +0000 From: Catalin Marinas To: Arnd Bergmann Cc: "linux-arm-kernel@lists.infradead.org" , Olof Johansson , "agraf@suse.de" , Will Deacon , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] arm64: Enable CONFIG_COMPAT also for 64k page size Message-ID: <20141205123116.GD28339@e104818-lin.cambridge.arm.com> References: <1417707993-82290-1-git-send-email-agraf@suse.de> <3551792.oHatG1W6W1@wuerfel> <20141205110507.GB28339@e104818-lin.cambridge.arm.com> <2131163.V0fUaF9isN@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2131163.V0fUaF9isN@wuerfel> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 05, 2014 at 12:24:49PM +0000, Arnd Bergmann wrote: > On Friday 05 December 2014 11:05:07 Catalin Marinas wrote: > > > > > Should we add support for 64k-pages in the arm32 kernel as well now? > > > > 32-bit LPAE doesn't support 64K pages but IIRC the classic MMU does > > (though I have to check whether it was optional). But it's not feasible > > to enable this in a 32-bit environment because of the memory wasted with > > large pages (on average 32KB per mapped file, possibly even more if you > > have lots of small files). > > That sounds like a tradeoff that some users might be willing to make. > > I remember that with ps3-linux, a lot of people wanted to enable 64k-pages > because the Cell processor has such a small number of TLB entries (256 or > 1024), but Linux only has around 200MB of memory available. I believe > there are arm32 machines with more RAM and fewer TLBs. I've heard that the WD MyCloud NAS (Cortex-A9 based) moved to 64K pages and they rebuilt the filesystem (which annoyed some people that were previously installing Debian packages directly, they now need recompilation). -- Catalin -- 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/