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From: Michal Hocko <mhocko@kernel.org>
To: linux-api@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	David Rientjes <rientjes@google.com>, Jan Kara <jack@suse.cz>
Subject: Re: [RFC PATCH 0/3] THP eligibility reporting via proc
Date: Fri, 7 Dec 2018 11:55:54 +0100
Message-ID: <20181207105554.GX1286@dhcp22.suse.cz> (raw)
In-Reply-To: <20181120103515.25280-1-mhocko@kernel.org>

On Tue 20-11-18 11:35:12, Michal Hocko wrote:
> Hi,
> this series of three patches aims at making THP eligibility reporting
> much more robust and long term sustainable. The trigger for the change
> is a regression report [1] and the long follow up discussion. In short
> the specific application didn't have good API to query whether a particular
> mapping can be backed by THP so it has used VMA flags to workaround that.
> These flags represent a deep internal state of VMAs and as such they should
> be used by userspace with a great deal of caution.
> 
> A similar has happened for [2] when users complained that VM_MIXEDMAP is
> no longer set on DAX mappings. Again a lack of a proper API led to an
> abuse.
> 
> The first patch in the series tries to emphasise that that the semantic
> of flags might change and any application consuming those should be really
> careful.
> 
> The remaining two patches provide a more suitable interface to address [1]
> and provide a consistent API to query the THP status both for each VMA
> and process wide as well.

Are there any other comments on these? I haven't heard any pushback so
far so I will re-send with RFC dropped early next week.

> 
> [1] http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com
> [2] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz
> 

-- 
Michal Hocko
SUSE Labs

      parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-20 10:35 Michal Hocko
2018-11-20 10:35 ` [RFC PATCH 1/3] mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps Michal Hocko
2018-11-20 10:51   ` Jan Kara
2018-11-20 11:41     ` Michal Hocko
2018-11-21  0:01     ` David Rientjes
2018-11-21  6:56       ` Michal Hocko
2018-11-20 18:32   ` Dan Williams
2018-11-21  7:05     ` Michal Hocko
2018-11-21 18:01       ` Mike Rapoport
2018-11-21 17:54   ` Mike Rapoport
2018-11-21 17:58     ` Michal Hocko
2018-11-23 13:47   ` Vlastimil Babka
2018-11-20 10:35 ` [RFC PATCH 2/3] mm, thp, proc: report THP eligibility for each vma Michal Hocko
2018-11-20 11:42   ` Michal Hocko
2018-11-23 15:07   ` Vlastimil Babka
2018-11-23 15:21     ` Michal Hocko
2018-11-23 15:24       ` Vlastimil Babka
2018-11-20 10:35 ` [RFC PATCH 3/3] mm, proc: report PR_SET_THP_DISABLE in proc Michal Hocko
2018-11-20 11:42   ` Michal Hocko
2018-11-23 15:49   ` Vlastimil Babka
2018-11-27  0:33   ` William Kucharski
2018-11-27 13:17     ` Michal Hocko
2018-11-27 14:50       ` William Kucharski
2018-11-27 16:25         ` Michal Hocko
2018-11-27 16:50         ` Vlastimil Babka
2018-11-27 17:06           ` William Kucharski
2018-12-07 10:55 ` Michal Hocko [this message]

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