From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752221AbdJEXcQ (ORCPT ); Thu, 5 Oct 2017 19:32:16 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:38837 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751083AbdJEXcM (ORCPT ); Thu, 5 Oct 2017 19:32:12 -0400 X-Google-Smtp-Source: AOwi7QA9mNMjHtujFzaLsvbm0rd3qDLnRrG8gguvKcY5IRE+Jzin/zVwtppxoDns94h5bFDmvNESMQ== Date: Thu, 5 Oct 2017 16:32:07 -0700 From: Alexei Starovoitov To: Laurent Dufour Cc: Paul McKenney , Peter Zijlstra , Andrew Morton , kirill@shutemov.name, Andi Kleen , Michal Hocko , dave@stgolabs.net, Jan Kara , Matthew Wilcox , Benjamin Herrenschmidt , Michael Ellerman , Paul Mackerras , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Will Deacon , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , linux-mm , haren@linux.vnet.ibm.com, Anshuman Khandual , npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, "x86@kernel.org" Subject: Re: [PATCH v3 00/20] Speculative page faults Message-ID: <20171005233206.vpg446q5k2r4g27r@ast-mbp> References: <670c9a22-cf5b-3fab-b2f2-a72fbd4451c8@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <670c9a22-cf5b-3fab-b2f2-a72fbd4451c8@linux.vnet.ibm.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 04, 2017 at 08:50:49AM +0200, Laurent Dufour wrote: > On 25/09/2017 18:27, Alexei Starovoitov wrote: > > On Mon, Sep 18, 2017 at 12:15 AM, Laurent Dufour > > wrote: > >> Despite the unprovable lockdep warning raised by Sergey, I didn't get any > >> feedback on this series. > >> > >> Is there a chance to get it moved upstream ? > > > > what is the status ? > > We're eagerly looking forward for this set to land, > > since we have several use cases for tracing that > > will build on top of this set as discussed at Plumbers. > > Hi Alexei, > > Based on Plumber's note [1], it sounds that the use case is tied to the BPF > tracing where a call tp find_vma() call will be made on a process's context > to fetch user space's symbols. > > Am I right ? > Is the find_vma() call made in the context of the process owning the mm > struct ? Hi Laurent, we're thinking about several use cases on top of your work. First one is translation of user address to file_handle where we need to do find_vma() from preempt_disabled context of bpf program. My understanding that srcu should solve that nicely. Second is making probe_read() to try harder when address is causing minor fault. We're thinking that find_vma() followed by some new light weight filemap_access() that doesn't sleep will do the trick. In both cases the program will be accessing current->mm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id D5E9F6B0033 for ; Thu, 5 Oct 2017 19:32:13 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id e26so21329854pfd.4 for ; Thu, 05 Oct 2017 16:32:13 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id b15sor35654pfm.129.2017.10.05.16.32.12 for (Google Transport Security); Thu, 05 Oct 2017 16:32:12 -0700 (PDT) Date: Thu, 5 Oct 2017 16:32:07 -0700 From: Alexei Starovoitov Subject: Re: [PATCH v3 00/20] Speculative page faults Message-ID: <20171005233206.vpg446q5k2r4g27r@ast-mbp> References: <670c9a22-cf5b-3fab-b2f2-a72fbd4451c8@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <670c9a22-cf5b-3fab-b2f2-a72fbd4451c8@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Laurent Dufour Cc: Paul McKenney , Peter Zijlstra , Andrew Morton , kirill@shutemov.name, Andi Kleen , Michal Hocko , dave@stgolabs.net, Jan Kara , Matthew Wilcox , Benjamin Herrenschmidt , Michael Ellerman , Paul Mackerras , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Will Deacon , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , linux-mm , haren@linux.vnet.ibm.com, Anshuman Khandual , npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, "x86@kernel.org" On Wed, Oct 04, 2017 at 08:50:49AM +0200, Laurent Dufour wrote: > On 25/09/2017 18:27, Alexei Starovoitov wrote: > > On Mon, Sep 18, 2017 at 12:15 AM, Laurent Dufour > > wrote: > >> Despite the unprovable lockdep warning raised by Sergey, I didn't get any > >> feedback on this series. > >> > >> Is there a chance to get it moved upstream ? > > > > what is the status ? > > We're eagerly looking forward for this set to land, > > since we have several use cases for tracing that > > will build on top of this set as discussed at Plumbers. > > Hi Alexei, > > Based on Plumber's note [1], it sounds that the use case is tied to the BPF > tracing where a call tp find_vma() call will be made on a process's context > to fetch user space's symbols. > > Am I right ? > Is the find_vma() call made in the context of the process owning the mm > struct ? Hi Laurent, we're thinking about several use cases on top of your work. First one is translation of user address to file_handle where we need to do find_vma() from preempt_disabled context of bpf program. My understanding that srcu should solve that nicely. Second is making probe_read() to try harder when address is causing minor fault. We're thinking that find_vma() followed by some new light weight filemap_access() that doesn't sleep will do the trick. In both cases the program will be accessing current->mm -- 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