linux-kernel - Re: [PATCH v3 0/3] idle memory tracking

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Message-ID: <20150429075853.GC1694@esperanza>
Date:	Wed, 29 Apr 2015 10:58:53 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Jonathan Corbet <corbet@....net>, <linux-api@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 0/3] idle memory tracking

Hi Minchan,

Thank you for taking a look at this patch set.

On Wed, Apr 29, 2015 at 12:57:22PM +0900, Minchan Kim wrote:
> On Tue, Apr 28, 2015 at 03:24:39PM +0300, Vladimir Davydov wrote:
> >  * /proc/kpageidle.  For each page this file contains a 64-bit number, which
> >    equals 1 if the page is idle or 0 otherwise, indexed by PFN. A page is
> 
> Why do we need 64bit per page to indicate just idle or not?

I don't think we need this, actually. I made this file 64 bit per page
only to conform to other /proc/kpage* files. Currently, I can't think of
any potential use for residual 63 bits, so personally I'm fine with 1
bit per page. If nobody comes with an idea about how > 1 bits could be
used, I'll switch /proc/kpageidle to a bitmask in the next iteration.

Thanks,
Vladimir
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