From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752678AbbKISlf (ORCPT ); Mon, 9 Nov 2015 13:41:35 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:34984 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752358AbbKISlB (ORCPT ); Mon, 9 Nov 2015 13:41:01 -0500 Date: Mon, 9 Nov 2015 19:40:57 +0100 (CET) From: Hans Ulli Kroll X-X-Sender: elektroman@T520.local To: Arnd Bergmann cc: Hans Ulli Kroll , Catalin Marinas , linux-arm-kernel@lists.infradead.org, Linus Torvalds , Linux Kernel Mailing List , Will Deacon Subject: Re: [GIT PULL] arm64 updates for 4.4 In-Reply-To: <5669629.gUNGHpWjD7@wuerfel> Message-ID: References: <20151104182508.GA28726@e104818-lin.cambridge.arm.com> <6253831.r99BEBrMgd@wuerfel> <5669629.gUNGHpWjD7@wuerfel> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 7 Nov 2015, Arnd Bergmann wrote: > On Saturday 07 November 2015 11:56:44 Hans Ulli Kroll wrote: > > On Fri, 6 Nov 2015, Arnd Bergmann wrote: > > > On Friday 06 November 2015 16:04:08 Catalin Marinas wrote: > > > > On Fri, Nov 06, 2015 at 10:57:58AM +0100, Arnd Bergmann wrote: > > > > > On Thursday 05 November 2015 18:27:18 Catalin Marinas wrote: > > > > > > On Wed, Nov 04, 2015 at 02:55:01PM -0800, Linus Torvalds wrote: > > > > > > > On Wed, Nov 4, 2015 at 10:25 AM, Catalin Marinas wrote: > > > > > > > It's good for single-process loads - if you do a lot of big fortran > > > > > > > jobs, or a lot of big database loads, and nothing else, you're fine. > > > > > > > > > > > > These are some of the arguments from the server camp: specific > > > > > > workloads. > > > > > > > > > > I think (a little overgeneralized), you want 4KB pages for any file > > > > > based mappings, > > > > > > > > In general, yes, but if the main/only workload on your server is mapping > > > > large db files, the memory usage cost may be amortised. > > > > > > This will still only do you good for a database that is read into memory > > > once and not written much, and at that point you can as well use hugepages. > > > > > > The problems for using 64kb page cache on file mappings are > > > > > > - while you normally want some readahead, the larger pages also result > > > in read-behind, so you have to actually transfer data from disk into > > > RAM without ever accessing it. > > > > > > - When you write the data, you have to write the full 64K page because > > > that is the granularity of your dirty bit tracking. > > > > > > So even if you don't care at all about memory consumption, you are > > > still transferring several times more data to and from your drives. > > > As mentioned that can be a win on some storage devices, but usually > > > it's a loss. > > > > > > > there is also a maybe a bigger problem. > > I know this from my Zyxel NAS540, this thing is build around the Mindspeed > > Comcerto 2000 SoC > > > > Zyxel is currently rolling back to support 4k page sizeses in upcommig > > 5.10 firmware release, because Minspeed did some stupid thing : > > > > It's not possible to use some standard ARMv7 toolchain and build your > > own/needed userspace tools. > > > > And this in change which causes the pain > > > > diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h > > -#define ELF_EXEC_PAGESIZE 4096 > > +#define ELF_EXEC_PAGESIZE (PAGE_SIZE) > > In ARM32 binutils, ELF_MAXPAGESIZE was changed last year to 64KB, so > binutils-2.25 or higher should support this by default, as long as you > recompile all user binaries. > Thanks for the hint ... > > The SoC is mostly build from off the shelf IP's > > SATA, NAND, SPI and so on > > The only thing which is completly braindead is MAC > > It's using some kind of VLAN tagging to support tree ports, > > only one descriptor chain for all three interfaces. > > You mean they used 64KB logical page sizes to work around a broken > ethernet MAC? > > Arnd > No. The MAC is some other issue : I think the main purpose of this design to use this SoC for Deep Packet Inspection in HW. They use also this MAC (or is't queue) for for en/decrypting traffic for the WIFI devices, in the sources it's called vwd. -> virtual wirelss divice. IP-Stack -> VWD -> WIFI-DEV FYI, Here is the Datasheed (only 4 Pages) http://downloads.codico.com/MISC/Newsletter/2013/2013_02/862xx-BRF-001-M_C2K.pdf But this is to much, to wrap my head around. Hans Ulli