On 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. > The approach is already implemented: https://lkml.org/lkml/2012/7/4/145 (add new MIGRATE_HOTREMOVE, not reuse MIGRATE_CMA) MIGRATE_HOTREMOVE and MIGRATE_CMA both have this problem: https://lkml.org/lkml/2012/7/5/83 R.I.P for this idea. zone->managed_pages(you proposed, but don't manage MIGRATE_HOTREMOVE nor MIGRATE_CMA) + proxy zone(handle all MIGRATE_HOTREMOVE, MIGRATE_CMA and ZONE_MOVABLE of the node) may be a good idea. Thanks, Lai -- 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>