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

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Message-ID: <20150203032628.GA4006@google.com>
Date:	Tue, 3 Feb 2015 03:26:28 +0000
From:	Petr Cermak <petrcermak@...omium.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	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)

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?
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