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From: Denys Vlasenko <vda.linux@googlemail.com>
To: Matt Mackall <mpm@selenic.com>
Subject: Re: [RFC][PATCH] /proc/<pid>/pmaps - memory maps in granularity of pages
Date: Wed, 5 Sep 2007 13:24:59 +0100
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Cc: linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       David Rientjes <rientjes@google.com>,
       John Berthels <jjberthels@gmail.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>
References: <20070814085204.GA10884@mail.ustc.edu.cn> <20070814162618.GV30556@waste.org>
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On Tuesday 14 August 2007 17:26, Matt Mackall wrote:
> On Tue, Aug 14, 2007 at 04:52:04PM +0800, Fengguang Wu wrote:
> > Here is a sample output:
> > 
> > # cat /proc/$$/pmaps
> > 080c9000-080f6000 rwxp 080c9000 00:00 0                                  [heap]
> > 32969   45      Y_A_P__ 1
...
> > f7de1000-f7de3000 rwxp 00011000 03:00 176630                             /lib/libnsl-2.3.6.so
> > 17      2       Y_A_P__ 1
> > [...]
> 
> That's a _lot_ of data to generate and parse. I doubt we can watch a
> larger app in realtime with this interface. And it doesn't give us
> physical page numbers either.


> > 080c9000-080f6000 rwxp 080c9000 00:00 0                                  [heap]
> > 32969   45      Y_A_P__ 1
    ^^^^^   ^^
> > f7dba000-f7dc3000 r-xp 00000000 03:00 176633                             /lib/libnss_files-2.3.6.so
                                    ^^ ^^ ^^^^^^

Since it's a new /proc file, we are not bound by compatibility.

Export *all* numbers in hex, and ensure that they are always even-chars wide
("fff" bad, "0fff" good). This way you can do binary<->string conversions
(both in kernel and in userspace) 8 bits per CPU cycle, or even faster.
--
vda
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