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 [thread overview]
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
next prev parent reply other threads:[~2019-05-21 12:15 UTC|newest]
Thread overview: 132+ 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 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
2019-05-30 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
2019-05-30 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
2019-05-30 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
2019-05-30 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 4:23 ` 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
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