On Tue, Nov 24, 2015 at 01:36:17PM +0100, Vlastimil Babka wrote:
> During migration, page_owner info is now copied with the rest of the page, so
> the stacktrace leading to free page allocation during migration is overwritten.
> For debugging purposes, it might be however useful to know that the page has
> been migrated since its initial allocation. This might happen many times during
> the lifetime for different reasons and fully tracking this, especially with
> stacktraces would incur extra memory costs. As a compromise, store and print
> the migrate_reason of the last migration that occured to the page. This is
> enough to distinguish compaction, numa balancing etc.
>
> Example page_owner entry after the patch:
>
> Page allocated via order 0, mask 0x24280ca
> PFN 669757 type Reclaimable Block 1308 type Reclaimable Flags UDLA
> [<ffffffff81164e8a>] __alloc_pages_nodemask+0x15a/0xa30
> [<ffffffff811ad435>] alloc_pages_vma+0xb5/0x250
> [<ffffffff8118ba54>] handle_mm_fault+0x1304/0x1820
> [<ffffffff81051213>] __do_page_fault+0x183/0x3f0
> [<ffffffff810514a2>] do_page_fault+0x22/0x30
> [<ffffffff81573ba8>] page_fault+0x28/0x30
> [<ffffffffffffffff>] 0xffffffffffffffff
> Page has been migrated, last migrate reason: compaction
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> include/linux/migrate.h | 6 +++++-
> include/linux/page_ext.h | 1 +
> include/linux/page_owner.h | 9 +++++++++
> mm/migrate.c | 20 +++++++++++++++++---
> mm/page_owner.c | 17 +++++++++++++++++
> 5 files changed, 49 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index cac1c09..ab92a8c 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -23,9 +23,13 @@ enum migrate_reason {
> MR_SYSCALL, /* also applies to cpusets */
> MR_MEMPOLICY_MBIND,
> MR_NUMA_MISPLACED,
> - MR_CMA
> + MR_CMA,
> + MR_TYPES
> };
>
> +/* In mm/migrate.c; also keep sync with include/trace/events/migrate.h */
> +extern char * migrate_reason_names[MR_TYPES];
> +
> #ifdef CONFIG_MIGRATION
>
> extern void putback_movable_pages(struct list_head *l);
> diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
> index 17f118a..e1fe7cf 100644
> --- a/include/linux/page_ext.h
> +++ b/include/linux/page_ext.h
> @@ -45,6 +45,7 @@ struct page_ext {
> unsigned int order;
> gfp_t gfp_mask;
> unsigned int nr_entries;
> + int last_migrate_reason;
> unsigned long trace_entries[8];
> #endif
> };
> diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
> index 6440daa..555893b 100644
> --- a/include/linux/page_owner.h
> +++ b/include/linux/page_owner.h
> @@ -12,6 +12,7 @@ extern void __set_page_owner(struct page *page,
> unsigned int order, gfp_t gfp_mask);
> extern gfp_t __get_page_owner_gfp(struct page *page);
> extern void __copy_page_owner(struct page *oldpage, struct page *newpage);
> +extern void __set_page_owner_migrate_reason(struct page *page, int reason);
>
> static inline void reset_page_owner(struct page *page, unsigned int order)
> {
> @@ -38,6 +39,11 @@ static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
> if (static_branch_unlikely(&page_owner_inited))
> __copy_page_owner(oldpage, newpage);
> }
> +static inline void set_page_owner_migrate_reason(struct page *page, int reason)
> +{
> + if (static_branch_unlikely(&page_owner_inited))
> + __set_page_owner_migrate_reason(page, reason);
> +}
> #else
> static inline void reset_page_owner(struct page *page, unsigned int order)
> {
> @@ -53,5 +59,8 @@ static inline gfp_t get_page_owner_gfp(struct page *page)
> static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
> {
> }
> +static inline void set_page_owner_migrate_reason(struct page *page, int reason)
> +{
> +}
> #endif /* CONFIG_PAGE_OWNER */
> #endif /* __LINUX_PAGE_OWNER_H */
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 863a0f1..12e9ab9 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -47,6 +47,16 @@
>
> #include "internal.h"
>
> +char *migrate_reason_names[MR_TYPES] = {
> + "compaction",
> + "memory_failure",
> + "memory_hotplug",
> + "syscall_or_cpuset",
> + "mempolicy_mbind",
> + "numa_misplaced",
> + "cma",
> +};
> +
> /*
> * migrate_prep() needs to be called before we start compiling a list of pages
> * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
> @@ -955,8 +965,10 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
> }
>
> rc = __unmap_and_move(page, newpage, force, mode);
> - if (rc == MIGRATEPAGE_SUCCESS)
> + if (rc == MIGRATEPAGE_SUCCESS) {
> put_new_page = NULL;
> + set_page_owner_migrate_reason(newpage, reason);
> + }
>
> out:
> if (rc != -EAGAIN) {
> @@ -1021,7 +1033,7 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
> static int unmap_and_move_huge_page(new_page_t get_new_page,
> free_page_t put_new_page, unsigned long private,
> struct page *hpage, int force,
> - enum migrate_mode mode)
> + enum migrate_mode mode, int reason)
> {
> int rc = -EAGAIN;
> int *result = NULL;
> @@ -1079,6 +1091,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> if (rc == MIGRATEPAGE_SUCCESS) {
> hugetlb_cgroup_migrate(hpage, new_hpage);
> put_new_page = NULL;
> + set_page_owner_migrate_reason(new_hpage, reason);
> }
>
> unlock_page(hpage);
> @@ -1151,7 +1164,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> if (PageHuge(page))
> rc = unmap_and_move_huge_page(get_new_page,
> put_new_page, private, page,
> - pass > 2, mode);
> + pass > 2, mode, reason);
> else
> rc = unmap_and_move(get_new_page, put_new_page,
> private, page, pass > 2, mode,
> @@ -1842,6 +1855,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
> set_page_memcg(new_page, page_memcg(page));
> set_page_memcg(page, NULL);
> page_remove_rmap(page, true);
> + set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
>
> spin_unlock(ptl);
> mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index f571e55..59fd6f1 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -6,6 +6,7 @@
> #include <linux/stacktrace.h>
> #include <linux/page_owner.h>
> #include <linux/jump_label.h>
> +#include <linux/migrate.h>
> #include "internal.h"
>
> static bool page_owner_disabled = true;
> @@ -73,10 +74,18 @@ void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
> page_ext->order = order;
> page_ext->gfp_mask = gfp_mask;
> page_ext->nr_entries = trace.nr_entries;
> + page_ext->last_migrate_reason = -1;
>
> __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
> }
>
> +void __set_page_owner_migrate_reason(struct page *page, int reason)
> +{
> + struct page_ext *page_ext = lookup_page_ext(page);
> +
> + page_ext->last_migrate_reason = reason;
> +}
> +
> gfp_t __get_page_owner_gfp(struct page *page)
> {
> struct page_ext *page_ext = lookup_page_ext(page);
> @@ -161,6 +170,14 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> if (ret >= count)
> goto err;
>
> + if (page_ext->last_migrate_reason != -1) {
> + ret += snprintf(kbuf + ret, count - ret,
> + "Page has been migrated, last migrate reason: %s\n",
> + migrate_reason_names[page_ext->last_migrate_reason]);
> + if (ret >= count)
> + goto err;
> + }
> +
migrate_reason_names is defined if CONFIG_MIGRATION is enabled so
it would cause build failure in case of !CONFIG_MIGRATION and
CONFIG_PAGE_OWNER.
Thanks.
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