From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f200.google.com (mail-ot0-f200.google.com [74.125.82.200]) by kanga.kvack.org (Postfix) with ESMTP id 2D9B06B000A for ; Fri, 29 Jun 2018 09:02:13 -0400 (EDT) Received: by mail-ot0-f200.google.com with SMTP id a1-v6so5379085oti.8 for ; Fri, 29 Jun 2018 06:02:13 -0700 (PDT) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id z22-v6si3320688oti.38.2018.06.29.06.02.07 for ; Fri, 29 Jun 2018 06:02:07 -0700 (PDT) Date: Fri, 29 Jun 2018 14:01:56 +0100 From: Mark Rutland Subject: Re: [PATCH v4 00/17] khwasan: kernel hardware assisted address sanitizer Message-ID: <20180629130155.e7ztz5ikxfl352ff@lakrids.cambridge.arm.com> References: <20180627160800.3dc7f9ee41c0badbf7342520@linux-foundation.org> <20180628124039.8a42ab5e2994fb2876ff4f75@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: Andrew Morton , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Will Deacon , Christoph Lameter , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev , linux-doc@vger.kernel.org, LKML , Linux ARM , linux-sparse@vger.kernel.org, Linux Memory Management List , Linux Kbuild mailing list , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya On Fri, Jun 29, 2018 at 02:45:08PM +0200, Andrey Konovalov wrote: > On Thu, Jun 28, 2018 at 9:40 PM, Andrew Morton > wrote: > > On Thu, 28 Jun 2018 20:29:07 +0200 Andrey Konovalov wrote: > > > >> >> Slab memory usage after boot [2]: > >> >> * ~40 kb for clean kernel > >> >> * ~105 kb + 1/8th shadow ~= 118 kb for KASAN > >> >> * ~47 kb + 1/16th shadow ~= 50 kb for KHWASAN > >> >> > >> >> Network performance [3]: > >> >> * 8.33 Gbits/sec for clean kernel > >> >> * 3.17 Gbits/sec for KASAN > >> >> * 2.85 Gbits/sec for KHWASAN > >> >> > >> >> Note, that KHWASAN (compared to KASAN) doesn't require quarantine. > >> >> > >> >> [1] Time before the ext4 driver is initialized. > >> >> [2] Measured as `cat /proc/meminfo | grep Slab`. > >> >> [3] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`. > >> > > >> > The above doesn't actually demonstrate the whole point of the > >> > patchset: to reduce KASAN's very high memory consumption? > >> > >> You mean that memory usage numbers collected after boot don't give a > >> representative picture of actual memory consumption on real workloads? > >> > >> What kind of memory consumption testing would you like to see? > > > > Well, 100kb or so is a teeny amount on virtually any machine. I'm > > assuming the savings are (much) more significant once the machine gets > > loaded up and doing work? > > So with clean kernel after boot we get 40 kb memory usage. With KASAN > it is ~120 kb, which is 200% overhead. With KHWASAN it's 50 kb, which > is 25% overhead. This should approximately scale to any amounts of > used slab memory. For example with 100 mb memory usage we would get > +200 mb for KASAN and +25 mb with KHWASAN. (And KASAN also requires > quarantine for better use-after-free detection). I can explicitly > mention the overhead in %s in the changelog. Could you elaborate on where that SLAB overhead comes from? IIUC that's not for the shadow itself (since it's allocated up-front and not accounted to SLAB), and that doesn't take into account the quarantine, so what's eating that space? Thanks, Mark.