On Thu, 26 Aug 2010 06:01:56 +0200 Michał Nazarewicz <m.nazarewicz@xxxxxxxxxxx> wrote: > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > 128MB...too big ? But it's depend on config. > > On embedded systems it may be like half of the RAM. Or a quarter. So bigger > granularity could be desired on some platforms. > > > IBM's ppc guys used 16MB section, and recently, a new interface to shrink > > the number of /sys files are added, maybe usable. > > > > Something good with this approach will be you can create "cma" memory > > before installing driver. > > That's how CMA works at the moment. But if I understand you correctly, what > you are proposing would allow to reserve memory *at* *runtime* long after system > has booted. This would be a nice feature as well though. > Yes, my proposal is that. > > But yes, complicated and need some works. > > > Ah, I need to clarify what I want to say. > > > > With compaction, it's helpful, but you can't get contiguous memory larger > > than MAX_ORDER, I think. To get memory larger than MAX_ORDER on demand, > > memory hot-plug code has almost all necessary things. > > I'll try to look at it then. > mm/memory_hotplug.c::offline_pages() does 1. disallow new allocation of memory in [start_pfn...end_pfn) 2. move all LRU pages to other regions than [start_pfn...end_pfn) 3. finally, mark all pages as PG_reserved (see __offline_isolated_pages()) What's required for cma will be a. remove _section_ limitation, which is done as BUG_ON(). b. replace 'step 3' with cma code. Maybe you can do similar just using compaction logic. The biggest difference will be 'step 1'. > > BTW, just curious...the memory for cma need not to be saved at > > hibernation ? Or drivers has to write its own hibernation ops by driver suspend > > udev or some ? > > Hibernation was not considered as of yet but I think it's device driver's > responsibility more then CMA's especially since it may make little sense to save > some of the buffers -- ie. no need to keep a frame from camera since it'll be > overwritten just after system wakes up from hibernation. It may also be better > to stop playback and resume it later on rather than trying to save decoder's > state. Again though, I haven't thought about hibernation as of yet. > Hmm, ok, use-case dependent and it's a job of a driver. Thanks, -Kame -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>