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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 6/7] mm: extend process_madvise syscall to support vector arrary
Date: Mon, 27 May 2019 16:49:40 +0900
Message-ID: <20190527074940.GB6879@google.com> (raw)
In-Reply-To: <20190521103726.GM32329@dhcp22.suse.cz>

On Tue, May 21, 2019 at 12:37:26PM +0200, Michal Hocko wrote:
> On Tue 21-05-19 19:26:13, Minchan Kim wrote:
> > On Tue, May 21, 2019 at 08:24:21AM +0200, Michal Hocko wrote:
> > > On Tue 21-05-19 11:48:20, Minchan Kim wrote:
> > > > On Mon, May 20, 2019 at 11:22:58AM +0200, Michal Hocko wrote:
> > > > > [Cc linux-api]
> > > > > 
> > > > > On Mon 20-05-19 12:52:53, Minchan Kim wrote:
> > > > > > Currently, process_madvise syscall works for only one address range
> > > > > > so user should call the syscall several times to give hints to
> > > > > > multiple address range.
> > > > > 
> > > > > Is that a problem? How big of a problem? Any numbers?
> > > > 
> > > > We easily have 2000+ vma so it's not trivial overhead. I will come up
> > > > with number in the description at respin.
> > > 
> > > Does this really have to be a fast operation? I would expect the monitor
> > > is by no means a fast path. The system call overhead is not what it used
> > > to be, sigh, but still for something that is not a hot path it should be
> > > tolerable, especially when the whole operation is quite expensive on its
> > > own (wrt. the syscall entry/exit).
> > 
> > What's different with process_vm_[readv|writev] and vmsplice?
> > If the range needed to be covered is a lot, vector operation makes senese
> > to me.
> 
> I am not saying that the vector API is wrong. All I am trying to say is
> that the benefit is not really clear so far. If you want to push it
> through then you should better get some supporting data.

I measured 1000 madvise syscall vs. a vector range syscall with 1000
ranges on ARM64 mordern device. Even though I saw 15% improvement but
absoluate gain is just 1ms so I don't think it's worth to support.
I will drop vector support at next revision.

Thanks for the review, Michal!

  reply index

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190520035254.57579-1-minchan@kernel.org>
     [not found] ` <20190520035254.57579-2-minchan@kernel.org>
2019-05-20  8:16   ` [RFC 1/7] mm: introduce MADV_COOL 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
     [not found] ` <20190520035254.57579-4-minchan@kernel.org>
2019-05-20  8:27   ` [RFC 3/7] mm: introduce MADV_COLD Michal Hocko
2019-05-20 23:00     ` Minchan Kim
2019-05-21  6:08       ` Michal Hocko
2019-05-21  9:13         ` Minchan Kim
     [not found] ` <20190520035254.57579-6-minchan@kernel.org>
2019-05-20  9:18   ` [RFC 5/7] mm: introduce external memory hinting API Michal Hocko
2019-05-21  2:41     ` Minchan Kim
2019-05-21  6:17       ` Michal Hocko
2019-05-21 10:32         ` Minchan Kim
     [not found] ` <20190520035254.57579-7-minchan@kernel.org>
2019-05-20  9:22   ` [RFC 6/7] mm: extend process_madvise syscall to support vector arrary 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 [this message]
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
     [not found] ` <20190520035254.57579-8-minchan@kernel.org>
2019-05-20  9:28   ` [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER 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
2019-05-20  9:28 ` [RFC 0/7] introduce memory hinting API for external process Michal Hocko
     [not found] ` <20190520164605.GA11665@cmpxchg.org>
     [not found]   ` <20190521043950.GJ10039@google.com>
2019-05-21  6:32     ` Michal Hocko
     [not found] ` <20190521014452.GA6738@bombadil.infradead.org>
2019-05-21  6:34   ` Michal Hocko
2019-05-21 12:53 ` Shakeel Butt
     [not found] ` <dbe801f0-4bbe-5f6e-9053-4b7deb38e235@arm.com>
     [not found]   ` <CAEe=Sxka3Q3vX+7aWUJGKicM+a9Px0rrusyL+5bB1w4ywF6N4Q@mail.gmail.com>
     [not found]     ` <1754d0ef-6756-d88b-f728-17b1fe5d5b07@arm.com>
2019-05-21 12:56       ` Shakeel Butt
2019-05-22  4:23         ` Brian Geffon

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