linux-kernel - Re: [RFC 0/7] introduce memory hinting API for external process

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Message-ID: <20190523130717.GA203306@google.com>
Date:   Thu, 23 May 2019 22:07:17 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Daniel Colascione <dancol@...gle.com>
Cc:     Christian Brauner <christian@...uner.io>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Murray <timmurray@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>, Jann Horn <jannh@...gle.com>
Subject: Re: [RFC 0/7] introduce memory hinting API for external process

On Wed, May 22, 2019 at 09:01:33AM -0700, Daniel Colascione wrote:
> On Wed, May 22, 2019 at 9:01 AM Christian Brauner <christian@...uner.io> wrote:
> >
> > On Wed, May 22, 2019 at 08:57:47AM -0700, Daniel Colascione wrote:
> > > On Wed, May 22, 2019 at 8:48 AM Christian Brauner <christian@...uner.io> wrote:
> > > >
> > > > On Wed, May 22, 2019 at 08:17:23AM -0700, Daniel Colascione wrote:
> > > > > On Wed, May 22, 2019 at 7:52 AM Christian Brauner <christian@...uner.io> wrote:
> > > > > > I'm not going to go into yet another long argument. I prefer pidfd_*.
> > > > >
> > > > > Ok. We're each allowed our opinion.
> > > > >
> > > > > > It's tied to the api, transparent for userspace, and disambiguates it
> > > > > > from process_vm_{read,write}v that both take a pid_t.
> > > > >
> > > > > Speaking of process_vm_readv and process_vm_writev: both have a
> > > > > currently-unused flags argument. Both should grow a flag that tells
> > > > > them to interpret the pid argument as a pidfd. Or do you support
> > > > > adding pidfd_vm_readv and pidfd_vm_writev system calls? If not, why
> > > > > should process_madvise be called pidfd_madvise while process_vm_readv
> > > > > isn't called pidfd_vm_readv?
> > > >
> > > > Actually, you should then do the same with process_madvise() and give it
> > > > a flag for that too if that's not too crazy.
> > >
> > > I don't know what you mean. My gut feeling is that for the sake of
> > > consistency, process_madvise, process_vm_readv, and process_vm_writev
> > > should all accept a first argument interpreted as either a numeric PID
> > > or a pidfd depending on a flag --- ideally the same flag. Is that what
> > > you have in mind?
> >
> > Yes. For the sake of consistency they should probably all default to
> > interpret as pid and if say PROCESS_{VM_}PIDFD is passed as flag
> > interpret as pidfd.
> 
> Sounds good to me!

Then, I want to change from pidfd to pid at next revsion and stick to
process_madvise as naming. Later, you guys could define PROCESS_PIDFD
flag and change all at once every process_xxx syscall friends.

If you are faster so that I see PROCESS_PIDFD earlier, I am happy to
use it.

Thanks.