From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-api@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>,
Tim Murray <timmurray@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Suren Baghdasaryan <surenb@google.com>,
Daniel Colascione <dancol@google.com>,
Shakeel Butt <shakeelb@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>,
jannh@google.com, oleg@redhat.com, christian@brauner.io,
oleksandr@redhat.com, hdanton@sina.com
Subject: Re: [RFCv2 5/6] mm: introduce external memory hinting API
Date: Fri, 31 May 2019 16:00:50 +0200 [thread overview]
Message-ID: <20190531140050.GS6896@dhcp22.suse.cz> (raw)
In-Reply-To: <20190531131859.GB195463@google.com>
On Fri 31-05-19 22:19:00, Minchan Kim wrote:
> On Fri, May 31, 2019 at 10:37:57AM +0200, Michal Hocko wrote:
> > On Fri 31-05-19 15:43:12, Minchan Kim wrote:
> > > There is some usecase that centralized userspace daemon want to give
> > > a memory hint like MADV_[COLD|PAGEEOUT] to other process. Android's
> > > ActivityManagerService is one of them.
> > >
> > > It's similar in spirit to madvise(MADV_WONTNEED), but the information
> > > required to make the reclaim decision is not known to the app. Instead,
> > > it is known to the centralized userspace daemon(ActivityManagerService),
> > > and that daemon must be able to initiate reclaim on its own without
> > > any app involvement.
> > >
> > > To solve the issue, this patch introduces new syscall process_madvise(2).
> > > It could give a hint to the exeternal process of pidfd.
> > >
> > > int process_madvise(int pidfd, void *addr, size_t length, int advise,
> > > unsigned long cookie, unsigned long flag);
> > >
> > > Since it could affect other process's address range, only privileged
> > > process(CAP_SYS_PTRACE) or something else(e.g., being the same UID)
> > > gives it the right to ptrace the process could use it successfully.
> > >
> > > The syscall has a cookie argument to privode atomicity(i.e., detect
> > > target process's address space change since monitor process has parsed
> > > the address range of target process so the operaion could fail in case
> > > of happening race). Although there is no interface to get a cookie
> > > at this moment, it could be useful to consider it as argument to avoid
> > > introducing another new syscall in future. It could support *atomicity*
> > > for disruptive hint(e.g., MADV_DONTNEED|FREE).
> > > flag argument is reserved for future use if we need to extend the API.
> >
> > Providing an API that is incomplete will not fly. Really. As this really
> > begs for much more discussion and it would be good to move on with the
> > core idea of the pro active memory memory management from userspace
> > usecase. Could you split out the core change so that we can move on and
> > leave the external for a later discussion. I believe this would lead to
> > a smoother integration.
>
> No problem but I need to understand what you want a little bit more because
> I thought this patchset is already step by step so if we reach the agreement
> of part of them like [1-5/6], it could be merged first.
>
> Could you say how you want to split the patchset for forward progress?
I would start with new madvise modes and once they are in a shape to be
merged then we can start the remote madvise API. I believe that even
local process reclaim modes are interesting and useful. I haven't heard
anybody objecting to them without having a remote API so far.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-05-31 14:00 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-31 6:43 [RFCv2 0/6] introduce memory hinting API for external process Minchan Kim
2019-05-31 6:43 ` [RFCv2 1/6] mm: introduce MADV_COLD Minchan Kim
2019-05-31 8:47 ` Michal Hocko
2019-05-31 13:39 ` Minchan Kim
2019-05-31 14:03 ` Michal Hocko
2019-05-31 14:34 ` Minchan Kim
2019-06-03 7:16 ` Michal Hocko
2019-06-03 15:43 ` Daniel Colascione
2019-06-03 17:27 ` Johannes Weiner
2019-06-03 20:32 ` Michal Hocko
2019-06-03 21:50 ` Johannes Weiner
2019-06-03 23:02 ` Minchan Kim
2019-06-04 6:56 ` Michal Hocko
2019-06-04 12:06 ` Johannes Weiner
2019-06-04 6:55 ` Michal Hocko
2019-06-04 4:26 ` Minchan Kim
2019-06-04 7:02 ` Michal Hocko
2019-05-31 6:43 ` [RFCv2 2/6] mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM Minchan Kim
2019-05-31 6:43 ` [RFCv2 3/6] mm: introduce MADV_PAGEOUT Minchan Kim
2019-05-31 8:50 ` Michal Hocko
2019-05-31 13:44 ` Minchan Kim
2019-05-31 16:59 ` Johannes Weiner
2019-05-31 23:14 ` Minchan Kim
2019-05-31 6:43 ` [RFCv2 4/6] mm: factor out madvise's core functionality Minchan Kim
2019-05-31 7:04 ` Oleksandr Natalenko
2019-05-31 13:12 ` Minchan Kim
2019-05-31 14:35 ` Oleksandr Natalenko
2019-05-31 23:29 ` Minchan Kim
2019-06-05 13:27 ` Oleksandr Natalenko
2019-06-10 10:12 ` Minchan Kim
2019-05-31 6:43 ` [RFCv2 5/6] mm: introduce external memory hinting API Minchan Kim
2019-05-31 8:37 ` Michal Hocko
2019-05-31 13:19 ` Minchan Kim
2019-05-31 14:00 ` Michal Hocko [this message]
2019-05-31 14:11 ` Minchan Kim
2019-05-31 17:35 ` Daniel Colascione
2019-05-31 6:43 ` [RFCv2 6/6] mm: extend process_madvise syscall to support vector arrary Minchan Kim
2019-05-31 10:06 ` Yann Droneaud
2019-05-31 23:18 ` Minchan Kim
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