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Date:   Tue, 27 Feb 2018 05:18:18 +0300
From:   "Dmitry V. Levin" <ldv@altlinux.org>
To:     Pavel Emelyanov <xemul@virtuozzo.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>, 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 <arnd@arndb.de>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Josh Triplett <josh@joshtriplett.org>,
        Jann Horn <jannh@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Andrei Vagin <avagin@openvz.org>
Subject: Re: [PATCH v5 0/4] vm: add a syscall to map a process memory into a
 pipe
Message-ID: <20180227021818.GA31386@altlinux.org>
Mail-Followup-To: Pavel Emelyanov <xemul@virtuozzo.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>, linux-mm@kvack.org,
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        linux-api@vger.kernel.org, criu@openvz.org, gdb@sourceware.org,
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        Arnd Bergmann <arnd@arndb.de>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Josh Triplett <josh@joshtriplett.org>, Jann Horn <jannh@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Andrei Vagin <avagin@openvz.org>
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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.c=
om> wrote:
> >=20
> >> This patches introduces new process_vmsplice system call that combines
> >> functionality of process_vm_read and vmsplice.
> >=20
> > 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?
>=20
> Yes, that's what bothers us a lot too :) I've tried to start with finding=
 out if anyone=20
> used the sys_read/write_process_vm() calls, but failed :( Does anybody kn=
ow how popular
> these syscalls are?

Well, process_vm_readv itself is quite popular, it's used by debuggers nowa=
days,
see e.g.
$ strace -qq -esignal=3Dnone -eprocess_vm_readv strace -qq -o/dev/null cat =
/dev/null


--=20
ldv

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