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From: Valdis.Kletnieks@vt.edu (Valdis.Kletnieks at vt.edu)
To: kernelnewbies@lists.kernelnewbies.org
Subject: Page fault in kernel code
Date: Wed, 10 Sep 2014 08:54:02 -0400	[thread overview]
Message-ID: <35026.1410353642@turing-police.cc.vt.edu> (raw)
In-Reply-To: Your message of "Wed, 10 Sep 2014 14:45:23 +0530." <CAJKgH8Dx1CStuWvgWXyrHEXA8LEDMv9PAZWNDph2AvQ=7owXTQ@mail.gmail.com>

On Wed, 10 Sep 2014 14:45:23 +0530, Manavendra Nath Manav said:

> But if the total RAM is limited (less than 896MB LOWMEM), for example as in
> embedded devices how the kernel code be kept in RAM all the time. Am I
> correct to assume that the kernel pre-fetches all pages when entering
> kernel mode from user mode?

No, kernel code is loaded by your boot loader, and *it stays there*.  Similarly,
if you modprobe something, the kernel allocates the page, loads the code,
and leaves it there.

Particularly in embedded devices, where you know all the modules the kernel may
need, it's common to just create a kernel with everything built in, no module
support, and when the system boots, it loads into memory and never moves again.

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  reply	other threads:[~2014-09-10 12:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAJKgH8Df51ZL-BaN_zBmtP=2tjxh5po6KWdbR1Q7LwiR2DZzTg@mail.gmail.com>
2014-09-09 13:23 ` Page fault in kernel code Manavendra Nath Manav
2014-09-09 14:25   ` Greg KH
2014-09-09 15:51   ` Valdis.Kletnieks at vt.edu
2014-09-09 16:54   ` Jeff Haran
2014-09-10  9:15     ` Manavendra Nath Manav
2014-09-10 12:54       ` Valdis.Kletnieks at vt.edu [this message]
2014-09-10 14:52         ` Manavendra Nath Manav
2014-09-11 12:03           ` Leon Romanovsky
2014-09-11 14:19             ` Christoph Lameter
2014-09-11 14:53             ` Miles MH Chen
2014-09-11 15:26               ` Leon Romanovsky

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