Messages in this thread | | | Date | Thu, 5 Dec 2002 13:43:54 +0530 | From | Suparna Bhattacharya <> | Subject | Re: Reserving physical memory at boot time |
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Crash dump after kexec also needs something similar, to prevent the new kernel from allocating pages holding the dump from the previous boot so that they aren't overwritten until the dump gets written out. The pages can be accessed(read) for the purpose of writeout. The Mission Critical implementation did this by patching the kernel to mark these pages as reserved early during bootup, much like the badmem mark pages as PG_Badmem.
There is a common theme running here of a "mark_claimed_pages" logic during early bootup, and "is_claimed_page" check at other places.
In the case of crash dump we have a fairly large number of pages to be marked out this way. The layout is available in the form of a map list, a pointer to which is passed on from the previous reboot.
So if we are looking for very minimal infrastructure which all of these can use, imposing a particular format in which such info (about unavailable memory) be passed in could become either less flexible or overgeneralized. Leaving the logic of identifying pages to be claimed (not available to the kernel for allocation) to the concerned subsystems appears to be a simpler and easier to extend approach.
Is there a good way to avoid embedding calls to early mem init code like mark_dump_pages, mark_bad_pages, mark_my_pages, etc and instead have each of these subsystems specify interest (a special section may be an overkill) so their corresponding routines get called ?
Regards Suparna
In article <Pine.LNX.4.33L2.0212031952530.7246-100000@dragon.pdx.osdl.net> Randy.Dunlap wrote: > On 3 Dec 2002, James Stevenson wrote:
> | On Tue, 2002-12-03 at 12:03, Duncan Sands wrote: > | > I would like to reserve a particular page of physical memory when > | > the kernel boots. By reserving I mean that no one else gets to read > | > from it or write to it: it is mine. Any suggestions for the best way > | > to go about this with a 2.5 kernel? > | > | try having a look for the linux badmem patches i belive they might do > | the same sort of thing.
> see http://badmem.sourceforge.net/
> -- > ~Randy
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-- Suparna Bhattacharya (suparna@in.ibm.com) Linux Technology Center IBM Software Labs, India
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