From: Matt Mackall <mpm@selenic.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Pavel Emelyanov <xemul@parallels.com>,
Hugh Dickins <hughd@google.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Michal Hocko <mhocko@suse.cz>, Mel Gorman <mgorman@suse.de>,
Johannes Weiner <hannes@cmpxchg.org>,
Linux MM <linux-mm@kvack.org>, Rik van Riel <riel@redhat.com>,
Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: [RFC PATCH 0/2] mm: Add ability to monitor task's memory changes
Date: Tue, 04 Dec 2012 18:38:57 -0600 [thread overview]
Message-ID: <1354667937.6733.233.camel@calx> (raw)
In-Reply-To: <20121204162411.700d4954.akpm@linux-foundation.org>
On Tue, 2012-12-04 at 16:24 -0800, Andrew Morton wrote:
> On Tue, 04 Dec 2012 18:17:08 -0600
> Matt Mackall <mpm@selenic.com> wrote:
>
> > On Tue, 2012-12-04 at 15:21 -0800, Andrew Morton wrote:
> > > On Tue, 04 Dec 2012 09:15:10 +0400
> > > Pavel Emelyanov <xemul@parallels.com> wrote:
> > >
> > > >
> > > > > Two alternatives come to mind:
> > > > >
> > > > > 1) Use /proc/pid/pagemap (Documentation/vm/pagemap.txt) in some
> > > > > fashion to determine which pages have been touched.
> >
> > [momentarily coming out of kernel retirement for old man rant]
> >
> > This is a popular interface anti-pattern.
> >
> > You shouldn't use an interface that gives you huge amount of STATE to
> > detect small amounts of CHANGE via manual differentiation.
>
> I'm not sure that's what checkpoint-restart will be doing. If we want
> to determine "which pages have been touched since the last checkpoint
> ten minutes ago" then that set of touched pages *is* state. And it's
> not "small"!
Yeah, there is definitely a middle-ground here between "I want
high-frequency updates" and "I want to see the whole picture".
The filesystem analogy is backups: we don't have any good way to say
"find me all files changed since yesterday" short of "find all files".
The closest thing is explicit snapshotting.
--
Mathematics is the supreme nostalgia of our time.
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next prev parent reply other threads:[~2012-12-05 0:39 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-30 17:55 [RFC PATCH 0/2] mm: Add ability to monitor task's memory changes Pavel Emelyanov
2012-11-30 17:55 ` [PATCH 1/2] mm: Mark VMA with VM_TRACE bit Pavel Emelyanov
2012-11-30 17:55 ` [PATCH 2/2] mm: Generate events when tasks change their memory Pavel Emelyanov
2012-12-03 23:42 ` Xiao Guangrong
2012-12-04 5:04 ` Pavel Emelyanov
2012-12-03 8:36 ` [RFC PATCH 0/2] mm: Add ability to monitor task's memory changes Glauber Costa
2012-12-03 20:16 ` Marcelo Tosatti
2012-12-04 7:39 ` Glauber Costa
2012-12-03 22:43 ` Andrew Morton
2012-12-04 5:15 ` Pavel Emelyanov
2012-12-04 23:21 ` Andrew Morton
2012-12-05 0:17 ` Matt Mackall
2012-12-05 0:24 ` Andrew Morton
2012-12-05 0:38 ` Matt Mackall [this message]
2012-12-05 9:53 ` Pavel Emelyanov
2012-12-05 22:06 ` Andrew Morton
2012-12-06 6:32 ` Pavel Emelyanov
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