From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrei Vagin Subject: Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a pipe Date: Wed, 28 Feb 2018 09:50:36 -0800 Message-ID: <20180228175035.GA20686@outlook.office365.com> References: <1515479453-14672-1-git-send-email-rppt@linux.vnet.ibm.com> <20180220164406.3ec34509376f16841dc66e34@linux-foundation.org> <3122ec5a-7f73-f6b4-33ea-8c10ef32e5b0@virtuozzo.com> <20180227021818.GA31386@altlinux.org> <627ac4f8-a52d-0582-0c9e-e70ea667fa7e@virtuozzo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Return-path: Content-Disposition: inline In-Reply-To: <627ac4f8-a52d-0582-0c9e-e70ea667fa7e@virtuozzo.com> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Emelyanov Cc: Andrew Morton , Mike Rapoport , Alexander Viro , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, criu@openvz.org, gdb@sourceware.org, devel@lists.open-mpi.org, rr-dev@mozilla.org, Arnd Bergmann , Michael Kerrisk , Thomas Gleixner , Josh Triplett , Jann Horn , Greg KH , Andrei Vagin List-Id: linux-api@vger.kernel.org On Wed, Feb 28, 2018 at 10:12:55AM +0300, Pavel Emelyanov wrote: > On 02/27/2018 05:18 AM, Dmitry V. Levin wrote: > > On Mon, Feb 26, 2018 at 12:02:25PM +0300, Pavel Emelyanov wrote: > >> On 02/21/2018 03:44 AM, Andrew Morton wrote: > >>> On Tue, 9 Jan 2018 08:30:49 +0200 Mike Rapoport wrote: > >>> > >>>> This patches introduces new process_vmsplice system call that combines > >>>> functionality of process_vm_read and vmsplice. > >>> > >>> All seems fairly strightforward. The big question is: do we know that > >>> people will actually use this, and get sufficient value from it to > >>> justify its addition? > >> > >> Yes, that's what bothers us a lot too :) I've tried to start with finding out if anyone > >> used the sys_read/write_process_vm() calls, but failed :( Does anybody know how popular > >> these syscalls are? > > > > Well, process_vm_readv itself is quite popular, it's used by debuggers nowadays, > > see e.g. > > $ strace -qq -esignal=none -eprocess_vm_readv strace -qq -o/dev/null cat /dev/null > > I see. Well, yes, this use-case will not benefit much from remote splice. How about more > interactive debug by, say, gdb? It may attach, then splice all the memory, then analyze > the victim code/data w/o copying it to its address space? Hmm, in this case, you probably will want to be able to map pipe pages into memory. > > -- Pavel