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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>