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From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.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>,
	linux-api@vger.kernel.org
Subject: Re: [RFC 5/7] mm: introduce external memory hinting API
Date: Tue, 21 May 2019 19:32:23 +0900
Message-ID: <20190521103223.GD219653@google.com> (raw)
In-Reply-To: <20190521061743.GC32329@dhcp22.suse.cz>

On Tue, May 21, 2019 at 08:17:43AM +0200, Michal Hocko wrote:
> On Tue 21-05-19 11:41:07, Minchan Kim wrote:
> > On Mon, May 20, 2019 at 11:18:29AM +0200, Michal Hocko wrote:
> > > [Cc linux-api]
> > > 
> > > On Mon 20-05-19 12:52:52, Minchan Kim wrote:
> > > > There is some usecase that centralized userspace daemon want to give
> > > > a memory hint like MADV_[COOL|COLD] 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.
> > > 
> > > Could you expand some more about how this all works? How does the
> > > centralized daemon track respective ranges? How does it synchronize
> > > against parallel modification of the address space etc.
> > 
> > Currently, we don't track each address ranges because we have two
> > policies at this moment:
> > 
> > 	deactive file pages and reclaim anonymous pages of the app.
> > 
> > Since the daemon has a ability to let background apps resume(IOW, process
> > will be run by the daemon) and both hints are non-disruptive stabilty point
> > of view, we are okay for the race.
> 
> Fair enough but the API should consider future usecases where this might
> be a problem. So we should really think about those potential scenarios
> now. If we are ok with that, fine, but then we should be explicit and
> document it that way. Essentially say that any sort of synchronization
> is supposed to be done by monitor. This will make the API less usable
> but maybe that is enough.

Okay, I will add more about that in the description.

>  
> > > > To solve the issue, this patch introduces new syscall process_madvise(2)
> > > > which works based on pidfd so it could give a hint to the exeternal
> > > > process.
> > > > 
> > > > int process_madvise(int pidfd, void *addr, size_t length, int advise);
> > > 
> > > OK, this makes some sense from the API point of view. When we have
> > > discussed that at LSFMM I was contemplating about something like that
> > > except the fd would be a VMA fd rather than the process. We could extend
> > > and reuse /proc/<pid>/map_files interface which doesn't support the
> > > anonymous memory right now. 
> > > 
> > > I am not saying this would be a better interface but I wanted to mention
> > > it here for a further discussion. One slight advantage would be that
> > > you know the exact object that you are operating on because you have a
> > > fd for the VMA and we would have a more straightforward way to reject
> > > operation if the underlying object has changed (e.g. unmapped and reused
> > > for a different mapping).
> > 
> > I agree your point. If I didn't miss something, such kinds of vma level
> > modify notification doesn't work even file mapped vma at this moment.
> > For anonymous vma, I think we could use userfaultfd, pontentially.
> > It would be great if someone want to do with disruptive hints like
> > MADV_DONTNEED.
> > 
> > I'd like to see it further enhancement after landing address range based
> > operation via limiting hints process_madvise supports to non-disruptive
> > only(e.g., MADV_[COOL|COLD]) so that we could catch up the usercase/workload
> > when someone want to extend the API.
> 
> So do you think we want both interfaces (process_madvise and madvisefd)?

What I have in mind is to extend process_madvise later like this

struct pr_madvise_param {
    int size;                       /* the size of this structure */
    union {
    	const struct iovec __user *vec; /* address range array */
	int fd;				/* supported from 6.0 */
    }
}

with introducing new hint Or-able PR_MADV_RANGE_FD, so that process_madvise
can go with fd instead of address range.


  reply index

Thread overview: 138+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  3:52 [RFC 0/7] introduce memory hinting API for external process Minchan Kim
2019-05-20  3:52 ` [RFC 1/7] mm: introduce MADV_COOL Minchan Kim
2019-05-20  8:16   ` Michal Hocko
2019-05-20  8:19     ` Michal Hocko
2019-05-20 15:08       ` Suren Baghdasaryan
2019-05-20 22:55       ` Minchan Kim
2019-05-20 22:54     ` Minchan Kim
2019-05-21  6:04       ` Michal Hocko
2019-05-21  9:11         ` Minchan Kim
2019-05-21 10:05           ` Michal Hocko
2019-05-28  8:53   ` Hillf Danton
2019-05-28 10:58   ` Minchan Kim
2019-05-20  3:52 ` [RFC 2/7] mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM Minchan Kim
2019-05-20 16:50   ` Johannes Weiner
2019-05-20 22:57     ` Minchan Kim
2019-05-20  3:52 ` [RFC 3/7] mm: introduce MADV_COLD Minchan Kim
2019-05-20  8:27   ` Michal Hocko
2019-05-20 23:00     ` Minchan Kim
2019-05-21  6:08       ` Michal Hocko
2019-05-21  9:13         ` Minchan Kim
2019-05-28 14:54   ` Hillf Danton
2019-05-30  0:45   ` Minchan Kim
2019-05-20  3:52 ` [RFC 4/7] mm: factor out madvise's core functionality Minchan Kim
2019-05-20 14:26   ` Oleksandr Natalenko
2019-05-21  1:26     ` Minchan Kim
2019-05-21  6:36       ` Oleksandr Natalenko
2019-05-21  6:50         ` Michal Hocko
2019-05-21  7:06           ` Oleksandr Natalenko
2019-05-21 10:52             ` Minchan Kim
2019-05-21 11:00               ` Michal Hocko
2019-05-21 11:24                 ` Minchan Kim
2019-05-21 11:32                   ` Michal Hocko
2019-05-21 10:49         ` Minchan Kim
2019-05-21 10:55           ` Michal Hocko
2019-05-20  3:52 ` [RFC 5/7] mm: introduce external memory hinting API Minchan Kim
2019-05-20  9:18   ` Michal Hocko
2019-05-21  2:41     ` Minchan Kim
2019-05-21  6:17       ` Michal Hocko
2019-05-21 10:32         ` Minchan Kim [this message]
2019-05-21  9:01   ` Christian Brauner
2019-05-21 11:35     ` Minchan Kim
2019-05-21 11:51       ` Christian Brauner
2019-05-21 15:31   ` Oleg Nesterov
2019-05-27  7:43     ` Minchan Kim
2019-05-27 15:12       ` Oleg Nesterov
2019-05-27 23:33         ` Minchan Kim
2019-05-28  7:23           ` Michal Hocko
2019-05-29  3:41   ` Hillf Danton
2019-05-30  0:38   ` Minchan Kim
2019-05-20  3:52 ` [RFC 6/7] mm: extend process_madvise syscall to support vector arrary Minchan Kim
2019-05-20  9:22   ` Michal Hocko
2019-05-21  2:48     ` Minchan Kim
2019-05-21  6:24       ` Michal Hocko
2019-05-21 10:26         ` Minchan Kim
2019-05-21 10:37           ` Michal Hocko
2019-05-27  7:49             ` Minchan Kim
2019-05-29 10:08               ` Daniel Colascione
2019-05-29 10:33                 ` Michal Hocko
2019-05-30  2:17                   ` Minchan Kim
2019-05-30  6:57                     ` Michal Hocko
2019-05-30  8:02                       ` Minchan Kim
2019-05-30 16:19                         ` Daniel Colascione
2019-05-30 18:47                         ` Michal Hocko
2019-05-29  4:14   ` Hillf Danton
2019-05-30  0:35   ` Minchan Kim
2019-05-20  3:52 ` [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER Minchan Kim
2019-05-20  9:28   ` Michal Hocko
2019-05-21  2:55     ` Minchan Kim
2019-05-21  6:26       ` Michal Hocko
2019-05-27  7:58         ` Minchan Kim
2019-05-27 12:44           ` Michal Hocko
2019-05-28  3:26             ` Minchan Kim
2019-05-28  6:29               ` Michal Hocko
2019-05-28  8:13                 ` Minchan Kim
2019-05-28  8:31                   ` Daniel Colascione
2019-05-28  8:49                     ` Minchan Kim
2019-05-28  9:08                       ` Michal Hocko
2019-05-28  9:39                         ` Daniel Colascione
2019-05-28 10:33                           ` Michal Hocko
2019-05-28 11:21                             ` Daniel Colascione
2019-05-28 11:49                               ` Michal Hocko
2019-05-28 12:11                                 ` Daniel Colascione
2019-05-28 12:32                                   ` Michal Hocko
2019-05-28 10:32                         ` Minchan Kim
2019-05-28 10:41                           ` Michal Hocko
2019-05-28 11:12                             ` Minchan Kim
2019-05-28 11:28                               ` Michal Hocko
2019-05-28 11:42                                 ` Daniel Colascione
2019-05-28 11:56                                   ` Michal Hocko
2019-05-28 12:18                                     ` Daniel Colascione
2019-05-28 12:38                                       ` Michal Hocko
2019-05-28 12:10                                   ` Minchan Kim
2019-05-28 11:44                                 ` Minchan Kim
2019-05-28 11:51                                   ` Daniel Colascione
2019-05-28 12:06                                   ` Michal Hocko
2019-05-28 12:22                                     ` Minchan Kim
2019-05-28 11:28                             ` Daniel Colascione
2019-05-21 15:33       ` Johannes Weiner
2019-05-22  1:50         ` Minchan Kim
2019-05-29  4:36   ` Hillf Danton
2019-05-30  1:00   ` Minchan Kim
2019-05-20  6:37 ` [RFC 0/7] introduce memory hinting API for external process Anshuman Khandual
2019-05-20 16:59   ` Tim Murray
2019-05-21  2:55     ` Anshuman Khandual
2019-05-21  5:14       ` Minchan Kim
2019-05-21 10:34       ` Michal Hocko
2019-05-28 10:50         ` Anshuman Khandual
2019-05-21 12:56       ` Shakeel Butt
2019-05-22  4:15         ` Brian Geffon
2019-05-22  4:23         ` Brian Geffon
2019-05-20  9:28 ` Michal Hocko
2019-05-20 14:42 ` Oleksandr Natalenko
2019-05-21  2:56   ` Minchan Kim
2019-05-20 16:46 ` Johannes Weiner
2019-05-21  4:39   ` Minchan Kim
2019-05-21  6:32     ` Michal Hocko
2019-05-21  1:44 ` Matthew Wilcox
2019-05-21  5:01   ` Minchan Kim
2019-05-21  6:34   ` Michal Hocko
2019-05-21  8:42 ` Christian Brauner
2019-05-21 11:05   ` Minchan Kim
2019-05-21 11:30     ` Christian Brauner
2019-05-21 11:39       ` Christian Brauner
2019-05-22  5:11         ` Daniel Colascione
2019-05-22  8:22           ` Christian Brauner
2019-05-22 13:16             ` Daniel Colascione
2019-05-22 14:52               ` Christian Brauner
2019-05-22 15:17                 ` Daniel Colascione
2019-05-22 15:48                   ` Christian Brauner
2019-05-22 15:57                     ` Daniel Colascione
2019-05-22 16:01                       ` Christian Brauner
2019-05-22 16:01                         ` Daniel Colascione
2019-05-23 13:07                           ` Minchan Kim
2019-05-27  8:06                             ` Minchan Kim
2019-05-21 11:41       ` Minchan Kim
2019-05-21 12:04         ` Christian Brauner
2019-05-21 12:15           ` Oleksandr Natalenko
2019-05-21 12:53 ` Shakeel Butt

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