Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Oleksandr Natalenko <oleksandr@redhat.com>
To: Christian Brauner <christian@brauner.io>
Cc: Minchan Kim <minchan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>, Michal Hocko <mhocko@suse.com>,
	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
Subject: Re: [RFC 0/7] introduce memory hinting API for external process
Date: Tue, 21 May 2019 14:15:42 +0200
Message-ID: <20190521121542.3hfvouyynw2haail@butterfly.localdomain> (raw)
In-Reply-To: <E01B155E-2FB4-4411-8725-3A3D7ADBE1D9@brauner.io>

On Tue, May 21, 2019 at 02:04:00PM +0200, Christian Brauner wrote:
> On May 21, 2019 1:41:20 PM GMT+02:00, Minchan Kim <minchan@kernel.org> wrote:
> >On Tue, May 21, 2019 at 01:30:32PM +0200, Christian Brauner wrote:
> >> On Tue, May 21, 2019 at 08:05:52PM +0900, Minchan Kim wrote:
> >> > On Tue, May 21, 2019 at 10:42:00AM +0200, Christian Brauner wrote:
> >> > > On Mon, May 20, 2019 at 12:52:47PM +0900, Minchan Kim wrote:
> >> > > > - Background
> >> > > > 
> >> > > > The Android terminology used for forking a new process and
> >starting an app
> >> > > > from scratch is a cold start, while resuming an existing app is
> >a hot start.
> >> > > > While we continually try to improve the performance of cold
> >starts, hot
> >> > > > starts will always be significantly less power hungry as well
> >as faster so
> >> > > > we are trying to make hot start more likely than cold start.
> >> > > > 
> >> > > > To increase hot start, Android userspace manages the order that
> >apps should
> >> > > > be killed in a process called ActivityManagerService.
> >ActivityManagerService
> >> > > > tracks every Android app or service that the user could be
> >interacting with
> >> > > > at any time and translates that into a ranked list for lmkd(low
> >memory
> >> > > > killer daemon). They are likely to be killed by lmkd if the
> >system has to
> >> > > > reclaim memory. In that sense they are similar to entries in
> >any other cache.
> >> > > > Those apps are kept alive for opportunistic performance
> >improvements but
> >> > > > those performance improvements will vary based on the memory
> >requirements of
> >> > > > individual workloads.
> >> > > > 
> >> > > > - Problem
> >> > > > 
> >> > > > Naturally, cached apps were dominant consumers of memory on the
> >system.
> >> > > > However, they were not significant consumers of swap even
> >though they are
> >> > > > good candidate for swap. Under investigation, swapping out only
> >begins
> >> > > > once the low zone watermark is hit and kswapd wakes up, but the
> >overall
> >> > > > allocation rate in the system might trip lmkd thresholds and
> >cause a cached
> >> > > > process to be killed(we measured performance swapping out vs.
> >zapping the
> >> > > > memory by killing a process. Unsurprisingly, zapping is 10x
> >times faster
> >> > > > even though we use zram which is much faster than real storage)
> >so kill
> >> > > > from lmkd will often satisfy the high zone watermark, resulting
> >in very
> >> > > > few pages actually being moved to swap.
> >> > > > 
> >> > > > - Approach
> >> > > > 
> >> > > > The approach we chose was to use a new interface to allow
> >userspace to
> >> > > > proactively reclaim entire processes by leveraging platform
> >information.
> >> > > > This allowed us to bypass the inaccuracy of the kernel’s LRUs
> >for pages
> >> > > > that are known to be cold from userspace and to avoid races
> >with lmkd
> >> > > > by reclaiming apps as soon as they entered the cached state.
> >Additionally,
> >> > > > it could provide many chances for platform to use much
> >information to
> >> > > > optimize memory efficiency.
> >> > > > 
> >> > > > IMHO we should spell it out that this patchset complements
> >MADV_WONTNEED
> >> > > > and MADV_FREE by adding non-destructive ways to gain some free
> >memory
> >> > > > space. MADV_COLD is similar to MADV_WONTNEED in a way that it
> >hints the
> >> > > > kernel that memory region is not currently needed and should be
> >reclaimed
> >> > > > immediately; MADV_COOL is similar to MADV_FREE in a way that it
> >hints the
> >> > > > kernel that memory region is not currently needed and should be
> >reclaimed
> >> > > > when memory pressure rises.
> >> > > > 
> >> > > > To achieve the goal, the patchset introduce two new options for
> >madvise.
> >> > > > One is MADV_COOL which will deactive activated pages and the
> >other is
> >> > > > MADV_COLD which will reclaim private pages instantly. These new
> >options
> >> > > > complement MADV_DONTNEED and MADV_FREE by adding
> >non-destructive ways to
> >> > > > gain some free memory space. MADV_COLD is similar to
> >MADV_DONTNEED in a way
> >> > > > that it hints the kernel that memory region is not currently
> >needed and
> >> > > > should be reclaimed immediately; MADV_COOL is similar to
> >MADV_FREE in a way
> >> > > > that it hints the kernel that memory region is not currently
> >needed and
> >> > > > should be reclaimed when memory pressure rises.
> >> > > > 
> >> > > > This approach is 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 a centralized userspace daemon, and
> >that daemon
> >> > > > must be able to initiate reclaim on its own without any app
> >involvement.
> >> > > > To solve the concern, this patch introduces new syscall -
> >> > > > 
> >> > > > 	struct pr_madvise_param {
> >> > > > 		int size;
> >> > > > 		const struct iovec *vec;
> >> > > > 	}
> >> > > > 
> >> > > > 	int process_madvise(int pidfd, ssize_t nr_elem, int *behavior,
> >> > > > 				struct pr_madvise_param *restuls,
> >> > > > 				struct pr_madvise_param *ranges,
> >> > > > 				unsigned long flags);
> >> > > > 
> >> > > > The syscall get pidfd to give hints to external process and
> >provides
> >> > > > pair of result/ranges vector arguments so that it could give
> >several
> >> > > > hints to each address range all at once.
> >> > > > 
> >> > > > I guess others have different ideas about the naming of syscall
> >and options
> >> > > > so feel free to suggest better naming.
> >> > > 
> >> > > Yes, all new syscalls making use of pidfds should be named
> >> > > pidfd_<action>. So please make this pidfd_madvise.
> >> > 
> >> > I don't have any particular preference but just wondering why pidfd
> >is
> >> > so special to have it as prefix of system call name.
> >> 
> >> It's a whole new API to address processes. We already have
> >> clone(CLONE_PIDFD) and pidfd_send_signal() as you have seen since you
> >> exported pidfd_to_pid(). And we're going to have pidfd_open(). Your
> >> syscall works only with pidfds so it's tied to this api as well so it
> >> should follow the naming scheme. This also makes life easier for
> >> userspace and is consistent.
> >
> >Okay. I will change the API name at next revision.
> >Thanks.
> 
> Thanks!
> Fwiw, there's been a similar patch by Oleksandr for pidfd_madvise I stumbled upon a few days back:
> https://gitlab.com/post-factum/pf-kernel/commit/0595f874a53fa898739ac315ddf208554d9dc897
> 
> He wanted to be cc'ed but I forgot.

Thanks :).

FWIW, since this submission is essentially a continuation of our discussion
involving my earlier KSM submissions here, I won't move my gitlab branch
forward and will be happy to assist with what we have here, be it
pidfd_madvise() or a set or /proc files (or smth else).

> 
> Christian
> 

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Senior Software Maintenance Engineer


  reply index

Thread overview: 138+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  3:52 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
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 [this message]
2019-05-21 12:53 ` Shakeel Butt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190521121542.3hfvouyynw2haail@butterfly.localdomain \
    --to=oleksandr@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=bgeffon@google.com \
    --cc=christian@brauner.io \
    --cc=dancol@google.com \
    --cc=hannes@cmpxchg.org \
    --cc=jannh@google.com \
    --cc=joel@joelfernandes.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@suse.com \
    --cc=minchan@kernel.org \
    --cc=shakeelb@google.com \
    --cc=sonnyrao@google.com \
    --cc=surenb@google.com \
    --cc=timmurray@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git