Hello, On Tuesday, June 14, 2011 8:30 PM Arnd Bergmann wrote: > On Tuesday 14 June 2011 18:58:35 Michal Nazarewicz wrote: > > On Tue, 14 Jun 2011 18:03:00 +0200, Arnd Bergmann wrote: > > > For all I know, that is something that is only true for a few very > > > special Samsung devices, > > > > Maybe. I'm just answering your question. :) > > > > Ah yes, I forgot that separate regions for different purposes could > > decrease fragmentation. > > That is indeed a good point, but having a good allocator algorithm > could also solve this. I don't know too much about these allocation > algorithms, but there are probably multiple working approaches to this. > > > > I would suggest going forward without having multiple regions: > > > > Is having support for multiple regions a bad thing? Frankly, > > removing this support will change code from reading context passed > > as argument to code reading context from global variable. Nothing > > is gained; functionality is lost. > > What is bad IMHO is making them the default, which forces the board > code to care about memory management details. I would much prefer > to have contiguous allocation parameters tuned automatically to just > work on most boards before we add ways to do board-specific hacks. 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). 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). Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
