Page fault in kernel code

[leon@leon.nu (Leon Romanovsky)]

On Wed, Sep 10, 2014 at 5:52 PM, Manavendra Nath Manav
<mnm.kernel@gmail.com> wrote:
>
> On 10-Sep-2014 6:24 pm, <Valdis.Kletnieks@vt.edu> wrote:
>>
>> 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.
>>
>
> Linux kernel memory is not page-able, but memory allocated through vmalloc
> can still cause page fault. How device drivers using vmalloc handle this?
Pages allocated via vmalloc call won't generate page-faults.

>
>
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-- 
Leon Romanovsky | Independent Linux Consultant
        www.leon.nu | leon at leon.nu