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

[Posted April 29, 2015 by corbet]

From:		Vladimir Davydov <vdavydov-AT-parallels.com>
To:		Minchan Kim <minchan-AT-kernel.org>
Subject:		Re: [PATCH v3 0/3] idle memory tracking
Date:		Wed, 29 Apr 2015 10:58:53 +0300
Message-ID:		<20150429075853.GC1694@esperanza>
Cc:		Andrew Morton <akpm-AT-linux-foundation.org>, Johannes Weiner <hannes-AT-cmpxchg.org>, Michal Hocko <mhocko-AT-suse.cz>, Greg Thelen <gthelen-AT-google.com>, Michel Lespinasse <walken-AT-google.com>, David Rientjes <rientjes-AT-google.com>, Pavel Emelyanov <xemul-AT-parallels.com>, Cyrill Gorcunov <gorcunov-AT-openvz.org>, Jonathan Corbet <corbet-AT-lwn.net>, <linux-api-AT-vger.kernel.org>, <linux-doc-AT-vger.kernel.org>, <linux-mm-AT-kvack.org>, <cgroups-AT-vger.kernel.org>, <linux-kernel-AT-vger.kernel.org>
Archive‑link:		Article

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