On 2012-11-28 16:29, Wen Congyang wrote: > At 11/28/2012 12:08 PM, Jiang Liu Wrote: >> On 2012-11-28 11:24, Bob Liu wrote: >>> 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); >>> } >>> }; >> Seems a good idea to reserve memory by reusing CMA logic, though need more >> investigation here. One of CMA goal is to ensure pages in CMA are really >> movable, and this patchset tries to achieve the same goal at a first glance. > > Hmm, I don't like to reuse CMA. Because CMA is used for DMA. If we reuse it > for movable memory, I think movable zone is enough. And the start address is > not acceptable, because we want to specify the start address for each node. > > I think we can implement movablecore_map like that: > 1. parse the parameter > 2. reserve the memory after efi_reserve_boot_services() This sounds good, but the code to reserve memory for movable nodes will be similar to dma_declare_contiguous(). > 3. release the memory in mem_init > > What about this? > > Thanks > Wen Congyang >> >> >> >> >> > > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
