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From: Michal Hocko <mhocko@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrea Arcangeli <aarcange@redhat.com>,
	mm-commits@vger.kernel.org, Linux-MM <linux-mm@kvack.org>
Subject: Re: incoming
Date: Wed, 25 Sep 2019 08:36:48 +0200
Message-ID: <20190925063648.GD23050@dhcp22.suse.cz> (raw)
In-Reply-To: <CAHk-=wgKqbpGTNFb_Uty59Za__D+psZE8gKCmDVHijpBgQx3LA@mail.gmail.com>

On Tue 24-09-19 08:34:20, Linus Torvalds wrote:
> On Tue, Sep 24, 2019 at 12:48 AM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > The patch proposed by David is really non trivial wrt. potential side
> > effects.
> 
> The thing is, that's not an argument when we know that the current
> state is garbage and has a lot of these non-trivial side effects that
> are bad.
> 
> So the patch by David _fixes_ a non-trivial bad side effect.
> 
> You can't then say "there may be other non-trivial side effects that I
> don't even know about" as an argument for saying it's bad. David at
> least has numbers and an argument for his patch.

All I am saying is that I am not able to wrap my head around this patch
to provide a competent Ack. I also believe that the fix is targetting a
wrong layer of the problem as explained in my review feedback. Appart
from reclaim/compaction interaction mentioned by Vlastimil, it seems
that it is an overly eager fallback to a remote node in the fast path
that is causing a large part of the problem as well. Kcompactd is not
eager enough to keep high order allocations ready for the fast path.
This is not specific to THP we have many other high order allocations
which are going to follow the same pattern, likely not visible in any
counters but still having performance implications.

Let's discuss technical details in the respective email thread

-- 
Michal Hocko
SUSE Labs


  reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23 22:31 incoming Andrew Morton
2019-09-24  0:55 ` incoming Linus Torvalds
2019-09-24  4:31   ` incoming Andrew Morton
2019-09-24  7:48     ` incoming Michal Hocko
2019-09-24 15:34       ` incoming Linus Torvalds
2019-09-25  6:36         ` Michal Hocko [this message]
2019-09-24 19:55       ` incoming Vlastimil Babka
  -- strict thread matches above, loose matches on Subject: below --
2020-02-21  4:00 incoming Andrew Morton
2020-02-21  4:03 ` incoming Andrew Morton
2020-02-21 18:21 ` incoming Linus Torvalds
2020-02-21 18:32   ` incoming Konstantin Ryabitsev
2020-02-21 19:33   ` incoming Linus Torvalds
2020-02-04  1:33 incoming Andrew Morton
2020-02-04  2:27 ` incoming Linus Torvalds
2020-02-04  2:46   ` incoming Andrew Morton
2020-02-04  3:11     ` incoming Linus Torvalds
2020-01-31  6:10 incoming Andrew Morton
2020-01-14  0:28 incoming Andrew Morton
2020-01-04 20:55 incoming Andrew Morton
2019-12-18  4:50 incoming Andrew Morton
2019-12-05  0:48 incoming Andrew Morton
2019-12-01  1:47 incoming Andrew Morton
2019-12-01  5:17 ` incoming James Bottomley
2019-12-01 21:07 ` incoming Linus Torvalds
2019-12-02  8:21   ` incoming Steven Price
2019-11-22  1:53 incoming Andrew Morton
2019-11-16  1:34 incoming Andrew Morton
2019-11-06  5:16 incoming Andrew Morton
2019-10-19  3:19 incoming Andrew Morton
2019-10-14 21:11 incoming Andrew Morton
2019-10-07  0:57 incoming Andrew Morton
2019-09-25 23:45 incoming Andrew Morton
2019-08-30 23:04 incoming Andrew Morton
2019-08-25  0:54 incoming Andrew Morton
     [not found] <20190716162536.bb52b8f34a8ecf5331a86a42@linux-foundation.org>
2019-07-17  8:47 ` incoming Vlastimil Babka
2019-07-17  8:57   ` incoming Bhaskar Chowdhury
2019-07-17 16:13   ` incoming Linus Torvalds
2019-07-17 17:09     ` incoming Christian Brauner
2019-07-17 18:13     ` incoming Vlastimil Babka
2007-05-02 22:02 incoming Andrew Morton
2007-05-02 22:31 ` incoming Benjamin Herrenschmidt
2007-05-03  7:55 ` incoming Russell King
2007-05-03  8:05   ` incoming Andrew Morton
2007-05-04 13:37 ` incoming Greg KH
2007-05-04 16:14   ` incoming Andrew Morton
2007-05-04 17:02     ` incoming Greg KH
2007-05-04 18:57     ` incoming Roland McGrath
2007-05-04 19:24       ` incoming Greg KH
2007-05-04 19:29         ` incoming Roland McGrath

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