From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a pipe Date: Wed, 28 Feb 2018 10:12:55 +0300 Message-ID: <627ac4f8-a52d-0582-0c9e-e70ea667fa7e@virtuozzo.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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180227021818.GA31386@altlinux.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: 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 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? -- Pavel