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Date:      Sat, 09 Jun 2012 12:46:53 +0300
From:      Mikolaj Golub <trociny@freebsd.org>
To:        Konstantin Belousov <kostikbel@gmail.com>
Cc:        Alan Cox <alc@freebsd.org>, Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, Robert Watson <rwatson@freebsd.org>, Ivan Voras <ivoras@freebsd.org>, freebsd-hackers@freebsd.org
Subject:   Re: SuperPages utilization survey
Message-ID:  <86k3zglsvm.fsf@kopusha.home.net>
In-Reply-To: <20120609090740.GL85127@deviant.kiev.zoral.com.ua> (Konstantin Belousov's message of "Sat, 9 Jun 2012 12:07:40 %2B0300")
References:  <jqac8f$6mn$1@dough.gmane.org> <alpine.BSF.2.00.1206011429160.20357@wojtek.tensor.gdynia.pl> <CAF-QHFXsi3SaF-rmFK-qM89LfnStKwRWN1-HRM4yg4Bt_SFAOg@mail.gmail.com> <86sje5kkl6.fsf@kopusha.home.net> <20120609083822.GJ85127@deviant.kiev.zoral.com.ua> <86obosluvk.fsf@kopusha.home.net> <20120609090740.GL85127@deviant.kiev.zoral.com.ua>

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On Sat, 9 Jun 2012 12:07:40 +0300 Konstantin Belousov wrote:

 KB> Well, if I see a report informing me that some 2M region contains 512 super
 KB> pages, how should I interpret it ? For me, it is only one superpage (mapping)
 KB> that can be created in one 2M region.

Well, if I see a report like below:

  PID              START                END PRT    RES PRES   SUP REF SHD  FL TP PATH
48568        0x800c00000        0x820c00000 rw- 131072    0 51712   2   0 --S df 

it tells me that for the region 0x800c00000-0x820c00000 (512Mb) we have 131072
* 4k = 512Mb resident and 51712 * 4k = 202Mb (a litle less than a half of the
region) promoted (mapped) to superpages.

If I had number of superpages here I would need additional knowledge (a
superpage size) to calculate how effectively superpages are used.

But actually, no much difference for me. To get a number of superpages is it
enough just to divide the result obtained counting normal-sized pages by
(2M/4k) factor?

-- 
Mikolaj Golub



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