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Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a pipe
- From: Pavel Emelyanov <xemul at virtuozzo dot com>
- To: Andrew Morton <akpm at linux-foundation dot org>, Mike Rapoport <rppt at linux dot vnet dot ibm dot com>, Alexander Viro <viro at zeniv dot linux dot org dot uk>, linux-mm at kvack dot org, linux-fsdevel at vger dot kernel dot org, linux-kernel at vger dot kernel dot org, linux-api at vger dot kernel dot org, criu at openvz dot org, gdb at sourceware dot org, devel at lists dot open-mpi dot org, rr-dev at mozilla dot org, Arnd Bergmann <arnd at arndb dot de>, Michael Kerrisk <mtk dot manpages at gmail dot com>, Thomas Gleixner <tglx at linutronix dot de>, Josh Triplett <josh at joshtriplett dot org>, Jann Horn <jannh at google dot com>, Greg KH <gregkh at linuxfoundation dot org>, Andrei Vagin <avagin at openvz dot org>
- Date: Wed, 28 Feb 2018 10:12:55 +0300
- Subject: Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a pipe
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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 <rppt@linux.vnet.ibm.com> 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