Messages in this thread Patch in this message | | | Subject | [PATCH] Make CONFIG_MIGRATION available for s390 | From | Gerald Schaefer <> | Date | Mon, 07 Jul 2008 18:41:46 +0200 |
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On Mon, 2008-07-07 at 19:24 +0900, Yasunori Goto wrote: > > include/linux/mempolicy.h already has a !NUMA section could we not just > > define policy_zone as 0 in that and leave this code unconditionally > > compiled? Perhaps also adding a NUMA_BUILD && to this 'if' should that > > be clearer. > > > Ah, yes. It's better. :-)
ok, the new patch below defines policy_zone as 0 in the !NUMA section. The compiler will automatically omit the if statement w/o NUMA in this case.
> > But this does make me feel uneasy. Are we really saying all memory on > > an s390 is migratable. That seems unlikely. As I understand the NUMA > > case, we only allow migration of memory in the last zone (last two if we > > have a MOVABLE zone) why are things different just because we have a > > single 'node'. Hmmm. I suspect strongly that something is missnamed > > more than there is a problem. > > If my understanding is correct, even if this policy_zone check is removed, > page isolation will just fail due to some busy pages. > In hotplug case, it means giving up of hotremoving, > and kernel must be rollback to make same condition of previous > starting offline_pages(). > This check means just "early" check, but not so effective for hotremoving, > I think....
It seems to me that this policy_zone check in vma_migratable() is not called at all for the offline_pages() case, only for some NUMA system calls that we don't support on s390. As Yasunori Goto said, page isolation checks should do the job for memory hotremove via offline_pages(), independent from any policy_zone setting. Any more thoughts on this?
Thanks, Gerald ---
Subject: [PATCH] Make CONFIG_MIGRATION available for s390
From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
We'd like to support CONFIG_MEMORY_HOTREMOVE on s390, which depends on CONFIG_MIGRATION. So far, CONFIG_MIGRATION is only available with NUMA support.
This patch makes CONFIG_MIGRATION selectable for architectures that define ARCH_ENABLE_MEMORY_HOTREMOVE. When MIGRATION is enabled w/o NUMA, the kernel won't compile because of a missing migrate() function in vm_operations_struct and a missing policy_zone reference in vma_migratable(). To avoid this, policy_zone is defined as 0 for !NUMA, and the vm_ops migrate() definition is moved from '#ifdef CONFIG_NUMA' to '#ifdef CONFIG_MIGRATION'.
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> ---
include/linux/mempolicy.h | 1 + include/linux/mm.h | 2 ++ mm/Kconfig | 2 +- 3 files changed, 4 insertions(+), 1 deletion(-)
Index: linux-2.6/include/linux/mm.h =================================================================== --- linux-2.6.orig/include/linux/mm.h +++ linux-2.6/include/linux/mm.h @@ -193,6 +193,8 @@ struct vm_operations_struct { */ struct mempolicy *(*get_policy)(struct vm_area_struct *vma, unsigned long addr); +#endif +#ifdef CONFIG_MIGRATION int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from, const nodemask_t *to, unsigned long flags); #endif Index: linux-2.6/mm/Kconfig =================================================================== --- linux-2.6.orig/mm/Kconfig +++ linux-2.6/mm/Kconfig @@ -174,7 +174,7 @@ config SPLIT_PTLOCK_CPUS config MIGRATION bool "Page migration" def_bool y - depends on NUMA + depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE help Allows the migration of the physical location of pages of processes while the virtual addresses are not changed. This is useful for Index: linux-2.6/include/linux/mempolicy.h =================================================================== --- linux-2.6.orig/include/linux/mempolicy.h +++ linux-2.6/include/linux/mempolicy.h @@ -222,6 +222,7 @@ extern int mpol_to_str(char *buffer, int #endif #else +#define policy_zone 0 struct mempolicy {}; static inline int mpol_equal(struct mempolicy *a, struct mempolicy *b)
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