On Tue, Nov 27, 2012 at 8:49 PM, Tang Chen <tangchen@xxxxxxxxxxxxxx> wrote: > On 11/27/2012 08:09 PM, Bob Liu wrote: >> >> On Tue, Nov 27, 2012 at 4:29 PM, Tang Chen<tangchen@xxxxxxxxxxxxxx> >> wrote: >>> >>> Hi Liu, >>> >>> >>> This feature is used in memory hotplug. >>> >>> In order to implement a whole node hotplug, we need to make sure the >>> node contains no kernel memory, because memory used by kernel could >>> not be migrated. (Since the kernel memory is directly mapped, >>> VA = PA + __PAGE_OFFSET. So the physical address could not be changed.) >>> >>> User could specify all the memory on a node to be movable, so that the >>> node could be hot-removed. >>> >> >> Thank you for your explanation. It's reasonable. >> >> But i think it's a bit duplicated with CMA, i'm not sure but maybe we >> can combine it with CMA which already in mainline? >> > Hi Liu, > > Thanks for your advice. :) > > CMA is Contiguous Memory Allocator, right? What I'm trying to do is > controlling where is the start of ZONE_MOVABLE of each node. Could > CMA do this job ? cma will not control the start of ZONE_MOVABLE of each node, but it can declare a memory that always movable and all non movable allocate request will not happen on that area. Currently cma use a boot parameter "cma=" to declare a memory size that always movable. I think it might fulfill your requirement if extending the boot parameter with a start address. more info at http://lwn.net/Articles/468044/ > > And also, after a short investigation, CMA seems need to base on > memblock. But we need to limit memblock not to allocate memory on > ZONE_MOVABLE. As a result, we need to know the ranges before memblock > could be used. I'm afraid we still need an approach to get the ranges, > such as a boot option, or from static ACPI tables such as SRAT/MPST. > Yes, it's based on memblock and with boot option. In setup_arch32() dma_contiguous_reserve(0); => will declare a cma area using memblock_reserve() > I'm don't know much about CMA for now. So if you have any better idea, > please share with us, thanks. :) My idea is reuse cma like below patch(even not compiled) and boot with "cma=size@start_address". I don't know whether it can work and whether suitable for your requirement, if not forgive me for this noises. diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c index 612afcc..564962a 100644 --- a/drivers/base/dma-contiguous.c +++ b/drivers/base/dma-contiguous.c @@ -59,11 +59,18 @@ struct cma *dma_contiguous_default_area; */ static const unsigned long size_bytes = CMA_SIZE_MBYTES * SZ_1M; static long size_cmdline = -1; +static long cma_start_cmdline = -1; static int __init early_cma(char *p) { + char *oldp; pr_debug("%s(%s)\n", __func__, p); + oldp = p; size_cmdline = memparse(p, &p); + + if (*p == '@') + cma_start_cmdline = memparse(p+1, &p); + printk("cma start:0x%x, size: 0x%x\n", size_cmdline, cma_start_cmdline); return 0; } early_param("cma", early_cma); @@ -127,8 +134,10 @@ void __init dma_contiguous_reserve(phys_addr_t limit) if (selected_size) { pr_debug("%s: reserving %ld MiB for global area\n", __func__, selected_size / SZ_1M); - - dma_declare_contiguous(NULL, selected_size, 0, limit); + if (cma_size_cmdline != -1) + dma_declare_contiguous(NULL, selected_size, cma_start_cmdline, limit); + else + dma_declare_contiguous(NULL, selected_size, 0, limit); } }; -- Regards, --Bob -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>