Question about memory management in L4 Fiasco O.C + L4re
foxmehdi at gmail.com
Mon Jul 20 16:36:52 CEST 2015
If I correctly understood, and If we suppose that an L4Linux instance
is started for example with this command line options:
... earlyprintk=1 em=64M ...
This means that a 64MB of physical memory region composed of a set of
contiguous physical frames is allocated to L4Linux, right?
L4Linux will use a part of this 64MB of physical memrory for its own kernel
the rest of physical memory space will be used by L4Linux to load
and allocate physical memory for them, right?
If a user-level program on top of L4Linux generates a page-fault.
Are the L4 Fiasco kernel and L4re involved in the execution flow to handle
Thank you very much for your clarification.
On Fri, Jul 17, 2015 at 10:36 AM, Mahdi Aichouch <foxmehdi at gmail.com> wrote:
> Hello Adam,
> The memory regions are exclusive. Specifying exactly which physical
>> memory an L4Linux is getting is currently not possible but I guess
>> you're using the numbers just as an example?
> Yes, I am giving these numbers as an example.
> However, is it possible to know what are the start address and the end address
> of a physical memory partition allocated to a L4Linux instance?
> The memory is completely mapped initially, so no page fault should
>> happen. As probably nobody will take it away again it should also stay
>> like this.
> Does this apply also to user-level programs executed on top of L4Linux.
> You can put showpfexc=1 on the cmdline to see any in-kernel page fault.
> There shouldn't be any (except in the outside wrapper code as I see
>> which can be changed by launching L4Linux with the eager_map flag).
> Could please give some explanation about what is the wrapper code? And Where to set the "eager_map flag" option?
> Thank you very much for your answer!
> Best regards,
> On Wed, Jul 15, 2015 at 11:53 AM, Mahdi Aichouch <foxmehdi at gmail.com>
>> I have some questions concerning memory management in Fiasco O.C + L4re.
>> I would like to test two L4Linux instances, and for each L4Linux
>> instance I want to reserve one static fixed physical memory partition.
>> For instance, one 128MB for the first L4Linux and one 128MB for the
>> Knowing that Fiasco O.C. uses "on demand paging" to allocate pages for
>> user tasks, is it possible that each partition of L4Linux could be
>> a static physical memory region composed of contiguous physical frames.
>> For instance, one memory region starting from 128MB to 256MB for the
>> first L4Linux,
>> and second memory region from 256MB to 512MB for the second L4Linux.
>> Each memory region is allocated exclusively to one L4Linux instance.
>> I would like to know if it is possible to load all the code + data of a
>> L4Linux instance
>> into its reserved memory partition, so no page fault will be encountered
>> during runtime.
>> Is it possible to tell me if these above operations could be realized in
>> Fiasco O.C and L4re?
>> If the answer is yes, is it possible to tell me what are the objects that
>> should be used or
>> adapted in order to implement these?
>> What are the issues that I should pay attention to?
>> Many thanks in advance for your answer.
>> Best regards,
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