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, 17 Oct 2018 09:05:31 +0200 [thread overview]
Message-ID: <20181017070531.GC18839@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.21.1810161416540.83080@chino.kir.corp.google.com>
On Tue 16-10-18 14:24:19, David Rientjes wrote:
> On Tue, 16 Oct 2018, Michal Hocko wrote:
>
> > > I don't understand the point of extending smaps with yet another line.
> >
> > Because abusing a vma flag part is just wrong. What are you going to do
> > when a next bug report states that the flag is set even though no
> > userspace has set it and that leads to some malfunctioning? Can you rule
> > that out? Even your abuse of the flag is surprising so why others
> > wouldn't be?
> >
>
> The flag has taken on the meaning of "thp disabled for this vma", how it
> is set is not the scope of the flag. If a thp is explicitly disabled from
> being eligible for thp, whether by madvise, prctl, or any future
> mechanism, it should use VM_NOHUGEPAGE or show_smap_vma_flags() needs to
> be modified.
No, this is not the meaning which is documented
nh - no-huge page advise flag
and as far as I know it is only you who has complained so far.
> > As I've said there are two things. Exporting PR_SET_THP_DISABLE to
> > userspace so that a 3rd party process can query it. I've already
> > explained why that might be useful. If you really insist on having
> > a per-vma field then let's do it properly now. Are you going to agree on
> > that? If yes, I am willing to spend my time on that but I am not going
> > to bother if this will lead to "I want my vma field abuse anyway".
>
> I think what you and I want is largely irrelevant :) What's important is
> that there are userspace implementations that query this today so
> continuing to support it as the way to determine if a vma has been thp
> disabled doesn't seem problematic and guarantees that userspace doesn't
> break.
Do you know of any other userspace except your usecase? Is there
anything fundamental that would prevent a proper API adoption for you?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-10-17 7:05 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
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 [this message]
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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