linux-kernel - Re: [PATCH v2 2/2] task_mmu: Add user-space support for resetting mm->hiwater

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Date:	Wed, 4 Feb 2015 00:51:03 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Petr Cermak <petrcermak@...omium.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	Primiano Tucci <primiano@...omium.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v2 2/2] task_mmu: Add user-space support for resetting
 mm->hiwater_rss (peak RSS)

Hello,

On Tue, Feb 03, 2015 at 03:26:28AM +0000, Petr Cermak wrote:
> On Mon, Jan 26, 2015 at 04:00:20PM -0800, David Rientjes wrote:
> > [...]
> > This is a result of allowing something external (process B) be able to
> > clear hwm so that you never knew the value went to 100MB.  That's the
> > definition of a race, I don't know how to explain it any better and making
> > any connection between clearing PG_referenced and mm->hiwater_rss is a
> > stretch.  This approach just makes mm->hiwater_rss meaningless.
> 
> I understand your concern, but I hope you agree that the functionality we
> are proposing would be very useful for profiling. Therefore, I suggest
> adding an extra resettable field to /proc/pid/status (e.g.
> resettable_hiwater_rss) instead. What is your view on this approach?

The idea would be very useful for measuring working set size for
efficient memory management in userside, which becomes very popular
with many platforms for embedded world with tight memory.

> 
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-- 
Kind regards,
Minchan Kim
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