From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227jzl0Ki+8FKVtl8sOzmicS34J8/Lw9SDpHKWojX5twDMjfX5vcDMC/YZ0rbVKVNSEEVmWf ARC-Seal: i=1; a=rsa-sha256; t=1519840251; cv=none; d=google.com; s=arc-20160816; b=jnmV+o32v+TkvntcfBftbe/8dT6Mf97TeHNqXVYV+FjipR2JAiK6WKr5zQvBc/k4SM FBe6PzeACeFOwyfiSgF5527IRwzGRN0eetJaOruPJozSmffd5513OvN3acC+WHL1DguJ LX8sK0L5ifY2UaH2xJRJ+utnYpzGtQuBMT11vugJUV6+bdxiTRoqalCtBpyXq2yrVIG2 GO9ufgAsSKyCTAa5NXBC5nysGs0IcE6n8B9JWXombXgjtbxv3SrNrrqundbhrnHk+iUc Bw5yn2GPaFmXrVCnjL8XbhuxnDsZkmu5KaLhFNQtfa8Yn+T/o5AZ5A4nRZh9ffpd6OYr qSkQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=spamdiagnosticmetadata:spamdiagnosticoutput:user-agent:in-reply-to :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:dkim-signature:arc-authentication-results; bh=B84sfxaZoVFX+9utguQ2qBWVGYiN/yFJvEBQPo1JSzw=; b=vO5MXjgFNn3+TvhMt1vDL0PDes7sCj5mljYzb3tTevHcqL91tOoab7STPC8h3DbRPU GICfui/W0JzpvPklBf3bUHHYg8voIutoPaE8LdkfsuJ+k3Cb4XTJJlxTb1ULJMz3POoK q0J9g+3DbdfGOB9gEhRuW7yesONv8/pprn10QX6cKHC+ClSJh9mdkRa3At/OTZzelsRe WMOKUcxiVY/HCipnA7o60/OLuuewx7SFfGibCazkag/Eq9y+vP1bmy7yUcdXMFjB81cv qlknWQXe2ybJ3WL8n4y8/JMiWyg8c1GwNnSBZOQ9/tRJfUnR+vVv5r57dvIx2jGz2OL1 OZIA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=selector1 header.b=UmrElVzo; spf=pass (google.com: domain of avagin@virtuozzo.com designates 40.107.4.131 as permitted sender) smtp.mailfrom=avagin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=selector1 header.b=UmrElVzo; spf=pass (google.com: domain of avagin@virtuozzo.com designates 40.107.4.131 as permitted sender) smtp.mailfrom=avagin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=avagin@virtuozzo.com; Date: Wed, 28 Feb 2018 09:50:36 -0800 From: Andrei Vagin 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 Subject: Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a pipe 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; 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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