From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH] mm: kill kmemcheck Date: Wed, 11 Mar 2015 10:43:29 -0400 Message-ID: <55005491.5080809@oracle.com> References: <1426074547-21888-1-git-send-email-sasha.levin@oracle.com> <20150311081909.552e2052@grimm.local.home> <55003666.3020100@oracle.com> <20150311084034.04ce6801@grimm.local.home> <55004595.7020304@oracle.com> <20150311102636.6b4110a8@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: LKML , linux-mm@kvack.org, netdev@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-crypto@vger.kernel.org To: Steven Rostedt Return-path: In-Reply-To: <20150311102636.6b4110a8@gandalf.local.home> Sender: linux-arch-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On 03/11/2015 10:26 AM, Steven Rostedt wrote: >> There's no real hurry to kill kmemcheck right now, but we do want to stop >> > supporting that in favour of KASan. > Understood, but the kernel is suppose to support older compilers. > Perhaps we can keep kmemcheck for now and say it's obsoleted if you > have a newer compiler. Because it will be a while before I upgrade my > compilers. I don't upgrade unless I have a good reason to do so. Not > sure KASan fulfills that requirement. It's not that there's a performance overhead with kmemcheck, it's the maintenance effort that we want to get rid of. The kernel should keep supporting old kernels, and after this kmemcheck removal your kernel will still keep working - this is more of a removal of a mostly unused feature that had hooks everywhere in the kernel. Did you actually find anything recently with kmemcheck? How do you deal with the 1 CPU limit and the massive performance hit? Could you try KASan for your use case and see if it potentially uncovers anything new? Thanks, Sasha From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f44.google.com (mail-oi0-f44.google.com [209.85.218.44]) by kanga.kvack.org (Postfix) with ESMTP id 51353900049 for ; Wed, 11 Mar 2015 10:43:38 -0400 (EDT) Received: by oibg201 with SMTP id g201so8135650oib.10 for ; Wed, 11 Mar 2015 07:43:38 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id zd5si2178050obc.94.2015.03.11.07.43.37 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 11 Mar 2015 07:43:37 -0700 (PDT) Message-ID: <55005491.5080809@oracle.com> Date: Wed, 11 Mar 2015 10:43:29 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: [PATCH] mm: kill kmemcheck References: <1426074547-21888-1-git-send-email-sasha.levin@oracle.com> <20150311081909.552e2052@grimm.local.home> <55003666.3020100@oracle.com> <20150311084034.04ce6801@grimm.local.home> <55004595.7020304@oracle.com> <20150311102636.6b4110a8@gandalf.local.home> In-Reply-To: <20150311102636.6b4110a8@gandalf.local.home> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt Cc: LKML , linux-mm@kvack.org, netdev@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-crypto@vger.kernel.org On 03/11/2015 10:26 AM, Steven Rostedt wrote: >> There's no real hurry to kill kmemcheck right now, but we do want to stop >> > supporting that in favour of KASan. > Understood, but the kernel is suppose to support older compilers. > Perhaps we can keep kmemcheck for now and say it's obsoleted if you > have a newer compiler. Because it will be a while before I upgrade my > compilers. I don't upgrade unless I have a good reason to do so. Not > sure KASan fulfills that requirement. It's not that there's a performance overhead with kmemcheck, it's the maintenance effort that we want to get rid of. The kernel should keep supporting old kernels, and after this kmemcheck removal your kernel will still keep working - this is more of a removal of a mostly unused feature that had hooks everywhere in the kernel. Did you actually find anything recently with kmemcheck? How do you deal with the 1 CPU limit and the massive performance hit? Could you try KASan for your use case and see if it potentially uncovers anything new? Thanks, Sasha -- 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