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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 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER
Date: Tue, 28 May 2019 17:13:51 +0900
Message-ID: <20190528081351.GA159710@google.com> (raw)
In-Reply-To: <20190528062947.GL1658@dhcp22.suse.cz>

On Tue, May 28, 2019 at 08:29:47AM +0200, Michal Hocko wrote:
> On Tue 28-05-19 12:26:32, Minchan Kim wrote:
> > On Mon, May 27, 2019 at 02:44:11PM +0200, Michal Hocko wrote:
> > > On Mon 27-05-19 16:58:11, Minchan Kim wrote:
> > > > On Tue, May 21, 2019 at 08:26:28AM +0200, Michal Hocko wrote:
> > > > > On Tue 21-05-19 11:55:33, Minchan Kim wrote:
> > > > > > On Mon, May 20, 2019 at 11:28:01AM +0200, Michal Hocko wrote:
> > > > > > > [cc linux-api]
> > > > > > > 
> > > > > > > On Mon 20-05-19 12:52:54, Minchan Kim wrote:
> > > > > > > > System could have much faster swap device like zRAM. In that case, swapping
> > > > > > > > is extremely cheaper than file-IO on the low-end storage.
> > > > > > > > In this configuration, userspace could handle different strategy for each
> > > > > > > > kinds of vma. IOW, they want to reclaim anonymous pages by MADV_COLD
> > > > > > > > while it keeps file-backed pages in inactive LRU by MADV_COOL because
> > > > > > > > file IO is more expensive in this case so want to keep them in memory
> > > > > > > > until memory pressure happens.
> > > > > > > > 
> > > > > > > > To support such strategy easier, this patch introduces
> > > > > > > > MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER options in madvise(2) like
> > > > > > > > that /proc/<pid>/clear_refs already has supported same filters.
> > > > > > > > They are filters could be Ored with other existing hints using top two bits
> > > > > > > > of (int behavior).
> > > > > > > 
> > > > > > > madvise operates on top of ranges and it is quite trivial to do the
> > > > > > > filtering from the userspace so why do we need any additional filtering?
> > > > > > > 
> > > > > > > > Once either of them is set, the hint could affect only the interested vma
> > > > > > > > either anonymous or file-backed.
> > > > > > > > 
> > > > > > > > With that, user could call a process_madvise syscall simply with a entire
> > > > > > > > range(0x0 - 0xFFFFFFFFFFFFFFFF) but either of MADV_ANONYMOUS_FILTER and
> > > > > > > > MADV_FILE_FILTER so there is no need to call the syscall range by range.
> > > > > > > 
> > > > > > > OK, so here is the reason you want that. The immediate question is why
> > > > > > > cannot the monitor do the filtering from the userspace. Slightly more
> > > > > > > work, all right, but less of an API to expose and that itself is a
> > > > > > > strong argument against.
> > > > > > 
> > > > > > What I should do if we don't have such filter option is to enumerate all of
> > > > > > vma via /proc/<pid>/maps and then parse every ranges and inode from string,
> > > > > > which would be painful for 2000+ vmas.
> > > > > 
> > > > > Painful is not an argument to add a new user API. If the existing API
> > > > > suits the purpose then it should be used. If it is not usable, we can
> > > > > think of a different way.
> > > > 
> > > > I measured 1568 vma parsing overhead of /proc/<pid>/maps in ARM64 modern
> > > > mobile CPU. It takes 60ms and 185ms on big cores depending on cpu governor.
> > > > It's never trivial.
> > > 
> > > This is not the only option. Have you tried to simply use
> > > /proc/<pid>/map_files interface? This will provide you with all the file
> > > backed mappings.
> > 
> > I compared maps vs. map_files with 3036 file-backed vma.
> > Test scenario is to dump all of vmas of the process and parse address
> > ranges.
> > For map_files, it's easy to parse each address range because directory name
> > itself is range. However, in case of maps, I need to parse each range
> > line by line so need to scan all of lines.
> > 
> > (maps cover additional non-file-backed vmas so nr_vma is a little bigger)
> > 
> > performance mode:
> > map_files: nr_vma 3036 usec 13387
> > maps     : nr_vma 3078 usec 12923
> > 
> > powersave mode:
> > 
> > map_files: nr_vma 3036 usec 52614
> > maps     : nr_vma 3078 usec 41089
> > 
> > map_files is slower than maps if we dump all of vmas. I guess directory
> > operation needs much more jobs(e.g., dentry lookup, instantiation)
> > compared to maps.
> 
> OK, that is somehow surprising. I am still not convinced the filter is a
> good idea though. The primary reason is that it encourages using madvise
> on a wide range without having a clue what the range contains. E.g. the
> full address range and rely the right thing will happen. Do we really
> want madvise to operate in that mode?

If user space daemon(e.g., activity manager service) could know a certain
process is bakground and idle for a while, yeb, that would be good option.

> 
> Btw. if we went with the per vma fd approach then you would get this
> feature automatically because map_files would refer to file backed
> mappings while map_anon could refer only to anonymous mappings.

The reason to add such filter option is to avoid the parsing overhead
so map_anon wouldn't be helpful.


> 
> -- 
> Michal Hocko
> SUSE Labs


  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
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 [this message]
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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