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From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.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: [patch v2] mm, thp: always specify ineligible vmas as nh in smaps
Date: Tue, 25 Sep 2018 15:04:06 -0700	[thread overview]
Message-ID: <20180925150406.872aab9f4f945193e5915d69@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1809251440001.94921@chino.kir.corp.google.com>

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?

  reply	other threads:[~2018-09-25 22:04 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 [this message]
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
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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