Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 08/10] mm: cma: Contiguous Memory Allocator added | Date | Wed, 15 Jun 2011 09:37:18 +0200 |
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On Wednesday 15 June 2011 09:11:39 Marek Szyprowski wrote: > I see your concerns, but I really wonder how to determine the properties > of the global/default cma pool. You definitely don't want to give all > available memory o CMA, because it will have negative impact on kernel > operation (kernel really needs to allocate unmovable pages from time to > time).
Exactly. This is a hard problem, so I would prefer to see a solution for coming up with reasonable defaults.
> The only solution I see now is to provide Kconfig entry to determine > the size of the global CMA pool, but this still have some issues, > especially for multi-board kernels (each board probably will have > different amount of RAM and different memory-consuming devices > available). It looks that each board startup code still might need to > tweak the size of CMA pool. I can add a kernel command line option for > it, but such solution also will not solve all the cases (afair there > was a discussion about kernel command line parameters for memory > configuration and the conclusion was that it should be avoided).
The command line option can be a last resort if the heuristics fail, but it's not much better than a fixed Kconfig setting.
How about a Kconfig option that defines the percentage of memory to set aside for contiguous allocations?
Arnd
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