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From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-api@vger.kernel.org
Subject: Re: [RFC PATCH] mm, proc: report PR_SET_THP_DISABLE in proc
Date: Wed, 3 Oct 2018 09:36:40 +0200	[thread overview]
Message-ID: <20181003073640.GF18290@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.21.1810021329260.87409@chino.kir.corp.google.com>

On Tue 02-10-18 13:29:42, David Rientjes wrote:
> On Tue, 2 Oct 2018, Michal Hocko wrote:
> 
> > On Wed 26-09-18 08:06:24, Michal Hocko wrote:
> > > On Tue 25-09-18 15:04:06, Andrew Morton wrote:
> > > > On Tue, 25 Sep 2018 14:45:19 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
> > > > 
> > > > > > > It is also used in 
> > > > > > > automated testing to ensure that vmas get disabled for thp appropriately 
> > > > > > > and we used "nh" since that is how PR_SET_THP_DISABLE previously enforced 
> > > > > > > this, and those tests now break.
> > > > > > 
> > > > > > This sounds like a bit of an abuse to me. It shows how an internal
> > > > > > implementation detail leaks out to the userspace which is something we
> > > > > > should try to avoid.
> > > > > > 
> > > > > 
> > > > > Well, it's already how this has worked for years before commit 
> > > > > 1860033237d4 broke it.  Changing the implementation in the kernel is fine 
> > > > > as long as you don't break userspace who relies on what is exported to it 
> > > > > and is the only way to determine if MADV_NOHUGEPAGE is preventing it from 
> > > > > being backed by hugepages.
> > > > 
> > > > 1860033237d4 was over a year ago so perhaps we don't need to be
> > > > too worried about restoring the old interface.  In which case
> > > > we have an opportunity to make improvements such as that suggested
> > > > by Michal?
> > > 
> > > Yeah, can we add a way to export PR_SET_THP_DISABLE to userspace
> > > somehow? E.g. /proc/<pid>/status. It is a process wide thing so
> > > reporting it per VMA sounds strange at best.
> > 
> > So how about this? (not tested yet but it should be pretty
> > straightforward)
> 
> Umm, prctl(PR_GET_THP_DISABLE)?

/me confused. I thought you want to query for the flag on a
_different_ process. 
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-10-03  7:36 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-24 17:55 [patch] mm, thp: always specify ineligible vmas as nh in smaps David Rientjes
2018-09-24 18:25 ` Vlastimil Babka
2018-09-24 19:17   ` David Rientjes
2018-09-24 19:30     ` [patch v2] " David Rientjes
2018-09-24 19:56       ` Michal Hocko
2018-09-24 20:02         ` Michal Hocko
2018-09-24 20:43           ` Vlastimil Babka
2018-09-25  5:50             ` Michal Hocko
2018-09-25 19:52             ` David Rientjes
2018-09-25 20:29               ` Michal Hocko
2018-09-25 21:45                 ` David Rientjes
2018-09-25 22:04                   ` Andrew Morton
2018-09-26  0:55                     ` David Rientjes
2018-09-26  6:06                     ` Michal Hocko
2018-10-02 11:28                       ` [RFC PATCH] mm, proc: report PR_SET_THP_DISABLE in proc Michal Hocko
2018-10-02 20:29                         ` David Rientjes
2018-10-03  7:36                           ` Michal Hocko [this message]
2018-10-03 22:51                             ` David Rientjes
2018-10-04  5:58                               ` Michal Hocko
2018-10-04  9:15                                 ` David Rientjes
2018-10-04  9:46                                   ` Michal Hocko
2018-10-04 18:34                                     ` David Rientjes
2018-10-09  8:33                                       ` Michal Hocko
2018-10-15 15:03                                         ` Michal Hocko
2018-10-15 22:25                                           ` David Rientjes
2018-10-16 10:48                                             ` Michal Hocko
2018-10-16 21:24                                               ` David Rientjes
2018-10-17  7:05                                                 ` Michal Hocko
2018-10-17 19:59                                                   ` David Rientjes
2018-10-18  7:00                                                     ` Michal Hocko
2018-11-14 13:23                                                       ` Michal Hocko
2018-11-14 21:41                                                         ` David Rientjes
2018-11-15  9:02                                                           ` Michal Hocko
2018-11-15  9:22                                                             ` Michal Hocko
2018-11-19 22:05                                                             ` David Rientjes
2018-11-20  7:48                                                               ` Michal Hocko
2018-10-03 17:33                           ` Mike Rapoport
2018-09-25 21:50               ` [patch v3] mm, thp: always specify disabled vmas as nh in smaps David Rientjes
2018-09-26  6:12                 ` Michal Hocko
2018-09-26  7:17                   ` Michal Hocko
2018-09-26  8:40                 ` Vlastimil Babka

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