From 95813b8faa0cd315f61a8b9d9c523792370b693e Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Thu, 17 Mar 2016 14:19:29 -0700 Subject: [PATCH] mm/page_ref: add tracepoint to track down page reference manipulation CMA allocation should be guaranteed to succeed by definition, but, unfortunately, it would be failed sometimes. It is hard to track down the problem, because it is related to page reference manipulation and we don't have any facility to analyze it. This patch adds tracepoints to track down page reference manipulation. With it, we can find exact reason of failure and can fix the problem. Following is an example of tracepoint output. (note: this example is stale version that printing flags as the number. Recent version will print it as human readable string.) <...>-9018 [004] 92.678375: page_ref_set: pfn=0x17ac9 flags=0x0 count=1 mapcount=0 mapping=(nil) mt=4 val=1 <...>-9018 [004] 92.678378: kernel_stack: => get_page_from_freelist (ffffffff81176659) => __alloc_pages_nodemask (ffffffff81176d22) => alloc_pages_vma (ffffffff811bf675) => handle_mm_fault (ffffffff8119e693) => __do_page_fault (ffffffff810631ea) => trace_do_page_fault (ffffffff81063543) => do_async_page_fault (ffffffff8105c40a) => async_page_fault (ffffffff817581d8) [snip] <...>-9018 [004] 92.678379: page_ref_mod: pfn=0x17ac9 flags=0x40048 count=2 mapcount=1 mapping=0xffff880015a78dc1 mt=4 val=1 [snip] ... ... <...>-9131 [001] 93.174468: test_pages_isolated: start_pfn=0x17800 end_pfn=0x17c00 fin_pfn=0x17ac9 ret=fail [snip] <...>-9018 [004] 93.174843: page_ref_mod_and_test: pfn=0x17ac9 flags=0x40068 count=0 mapcount=0 mapping=0xffff880015a78dc1 mt=4 val=-1 ret=1 => release_pages (ffffffff8117c9e4) => free_pages_and_swap_cache (ffffffff811b0697) => tlb_flush_mmu_free (ffffffff81199616) => tlb_finish_mmu (ffffffff8119a62c) => exit_mmap (ffffffff811a53f7) => mmput (ffffffff81073f47) => do_exit (ffffffff810794e9) => do_group_exit (ffffffff81079def) => SyS_exit_group (ffffffff81079e74) => entry_SYSCALL_64_fastpath (ffffffff817560b6) This output shows that problem comes from exit path. In exit path, to improve performance, pages are not freed immediately. They are gathered and processed by batch. During this process, migration cannot be possible and CMA allocation is failed. This problem is hard to find without this page reference tracepoint facility. Enabling this feature bloat kernel text 30 KB in my configuration. text data bss dec hex filename 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled Note that, due to header file dependency problem between mm.h and tracepoint.h, this feature has to open code the static key functions for tracepoints. Proposed by Steven Rostedt in following link. https://lkml.org/lkml/2015/12/9/699 [arnd@arndb.de: crypto/async_pq: use __free_page() instead of put_page()] [iamjoonsoo.kim@lge.com: fix build failure for xtensa] [akpm@linux-foundation.org: tweak Kconfig text, per Vlastimil] Signed-off-by: Joonsoo Kim Acked-by: Michal Nazarewicz Acked-by: Vlastimil Babka Cc: Minchan Kim Cc: Mel Gorman Cc: "Kirill A. Shutemov" Cc: Sergey Senozhatsky Acked-by: Steven Rostedt Signed-off-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- crypto/async_tx/async_pq.c | 2 +- include/linux/page_ref.h | 98 +++++++++++++++++++++-- include/trace/events/page_ref.h | 134 ++++++++++++++++++++++++++++++++ mm/Kconfig.debug | 13 ++++ mm/Makefile | 1 + mm/debug_page_ref.c | 54 +++++++++++++ 6 files changed, 296 insertions(+), 6 deletions(-) create mode 100644 include/trace/events/page_ref.h create mode 100644 mm/debug_page_ref.c diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c index c0748bbd4c08..08b3ac68952b 100644 --- a/crypto/async_tx/async_pq.c +++ b/crypto/async_tx/async_pq.c @@ -444,7 +444,7 @@ static int __init async_pq_init(void) static void __exit async_pq_exit(void) { - put_page(pq_scribble_page); + __free_page(pq_scribble_page); } module_init(async_pq_init); diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 30f5817f6b8e..e596d5d9540e 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -4,6 +4,62 @@ #include #include #include +#include + +extern struct tracepoint __tracepoint_page_ref_set; +extern struct tracepoint __tracepoint_page_ref_mod; +extern struct tracepoint __tracepoint_page_ref_mod_and_test; +extern struct tracepoint __tracepoint_page_ref_mod_and_return; +extern struct tracepoint __tracepoint_page_ref_mod_unless; +extern struct tracepoint __tracepoint_page_ref_freeze; +extern struct tracepoint __tracepoint_page_ref_unfreeze; + +#ifdef CONFIG_DEBUG_PAGE_REF + +/* + * Ideally we would want to use the trace__enabled() helper + * functions. But due to include header file issues, that is not + * feasible. Instead we have to open code the static key functions. + * + * See trace_##name##_enabled(void) in include/linux/tracepoint.h + */ +#define page_ref_tracepoint_active(t) static_key_false(&(t).key) + +extern void __page_ref_set(struct page *page, int v); +extern void __page_ref_mod(struct page *page, int v); +extern void __page_ref_mod_and_test(struct page *page, int v, int ret); +extern void __page_ref_mod_and_return(struct page *page, int v, int ret); +extern void __page_ref_mod_unless(struct page *page, int v, int u); +extern void __page_ref_freeze(struct page *page, int v, int ret); +extern void __page_ref_unfreeze(struct page *page, int v); + +#else + +#define page_ref_tracepoint_active(t) false + +static inline void __page_ref_set(struct page *page, int v) +{ +} +static inline void __page_ref_mod(struct page *page, int v) +{ +} +static inline void __page_ref_mod_and_test(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_mod_and_return(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_mod_unless(struct page *page, int v, int u) +{ +} +static inline void __page_ref_freeze(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_unfreeze(struct page *page, int v) +{ +} + +#endif static inline int page_ref_count(struct page *page) { @@ -18,6 +74,8 @@ static inline int page_count(struct page *page) static inline void set_page_count(struct page *page, int v) { atomic_set(&page->_count, v); + if (page_ref_tracepoint_active(__tracepoint_page_ref_set)) + __page_ref_set(page, v); } /* @@ -32,46 +90,74 @@ static inline void init_page_count(struct page *page) static inline void page_ref_add(struct page *page, int nr) { atomic_add(nr, &page->_count); + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod)) + __page_ref_mod(page, nr); } static inline void page_ref_sub(struct page *page, int nr) { atomic_sub(nr, &page->_count); + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod)) + __page_ref_mod(page, -nr); } static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_count); + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod)) + __page_ref_mod(page, 1); } static inline void page_ref_dec(struct page *page) { atomic_dec(&page->_count); + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod)) + __page_ref_mod(page, -1); } static inline int page_ref_sub_and_test(struct page *page, int nr) { - return atomic_sub_and_test(nr, &page->_count); + int ret = atomic_sub_and_test(nr, &page->_count); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test)) + __page_ref_mod_and_test(page, -nr, ret); + return ret; } static inline int page_ref_dec_and_test(struct page *page) { - return atomic_dec_and_test(&page->_count); + int ret = atomic_dec_and_test(&page->_count); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test)) + __page_ref_mod_and_test(page, -1, ret); + return ret; } static inline int page_ref_dec_return(struct page *page) { - return atomic_dec_return(&page->_count); + int ret = atomic_dec_return(&page->_count); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return)) + __page_ref_mod_and_return(page, -1, ret); + return ret; } static inline int page_ref_add_unless(struct page *page, int nr, int u) { - return atomic_add_unless(&page->_count, nr, u); + int ret = atomic_add_unless(&page->_count, nr, u); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_unless)) + __page_ref_mod_unless(page, nr, ret); + return ret; } static inline int page_ref_freeze(struct page *page, int count) { - return likely(atomic_cmpxchg(&page->_count, count, 0) == count); + int ret = likely(atomic_cmpxchg(&page->_count, count, 0) == count); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_freeze)) + __page_ref_freeze(page, count, ret); + return ret; } static inline void page_ref_unfreeze(struct page *page, int count) @@ -80,6 +166,8 @@ static inline void page_ref_unfreeze(struct page *page, int count) VM_BUG_ON(count == 0); atomic_set(&page->_count, count); + if (page_ref_tracepoint_active(__tracepoint_page_ref_unfreeze)) + __page_ref_unfreeze(page, count); } #endif diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h new file mode 100644 index 000000000000..81001f8b0db4 --- /dev/null +++ b/include/trace/events/page_ref.h @@ -0,0 +1,134 @@ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM page_ref + +#if !defined(_TRACE_PAGE_REF_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_PAGE_REF_H + +#include +#include +#include +#include + +DECLARE_EVENT_CLASS(page_ref_mod_template, + + TP_PROTO(struct page *page, int v), + + TP_ARGS(page, v), + + TP_STRUCT__entry( + __field(unsigned long, pfn) + __field(unsigned long, flags) + __field(int, count) + __field(int, mapcount) + __field(void *, mapping) + __field(int, mt) + __field(int, val) + ), + + TP_fast_assign( + __entry->pfn = page_to_pfn(page); + __entry->flags = page->flags; + __entry->count = page_ref_count(page); + __entry->mapcount = page_mapcount(page); + __entry->mapping = page->mapping; + __entry->mt = get_pageblock_migratetype(page); + __entry->val = v; + ), + + TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d", + __entry->pfn, + show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)), + __entry->count, + __entry->mapcount, __entry->mapping, __entry->mt, + __entry->val) +); + +DEFINE_EVENT(page_ref_mod_template, page_ref_set, + + TP_PROTO(struct page *page, int v), + + TP_ARGS(page, v) +); + +DEFINE_EVENT(page_ref_mod_template, page_ref_mod, + + TP_PROTO(struct page *page, int v), + + TP_ARGS(page, v) +); + +DECLARE_EVENT_CLASS(page_ref_mod_and_test_template, + + TP_PROTO(struct page *page, int v, int ret), + + TP_ARGS(page, v, ret), + + TP_STRUCT__entry( + __field(unsigned long, pfn) + __field(unsigned long, flags) + __field(int, count) + __field(int, mapcount) + __field(void *, mapping) + __field(int, mt) + __field(int, val) + __field(int, ret) + ), + + TP_fast_assign( + __entry->pfn = page_to_pfn(page); + __entry->flags = page->flags; + __entry->count = page_ref_count(page); + __entry->mapcount = page_mapcount(page); + __entry->mapping = page->mapping; + __entry->mt = get_pageblock_migratetype(page); + __entry->val = v; + __entry->ret = ret; + ), + + TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d", + __entry->pfn, + show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)), + __entry->count, + __entry->mapcount, __entry->mapping, __entry->mt, + __entry->val, __entry->ret) +); + +DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_and_test, + + TP_PROTO(struct page *page, int v, int ret), + + TP_ARGS(page, v, ret) +); + +DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_and_return, + + TP_PROTO(struct page *page, int v, int ret), + + TP_ARGS(page, v, ret) +); + +DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_unless, + + TP_PROTO(struct page *page, int v, int ret), + + TP_ARGS(page, v, ret) +); + +DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_freeze, + + TP_PROTO(struct page *page, int v, int ret), + + TP_ARGS(page, v, ret) +); + +DEFINE_EVENT(page_ref_mod_template, page_ref_unfreeze, + + TP_PROTO(struct page *page, int v), + + TP_ARGS(page, v) +); + +#endif /* _TRACE_PAGE_COUNT_H */ + +/* This part must be outside protection */ +#include diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 5c50b238b770..22f4cd96acb0 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -79,3 +79,16 @@ config PAGE_POISONING_ZERO Enabling page poisoning with this option will disable hibernation If unsure, say N + bool + +config DEBUG_PAGE_REF + bool "Enable tracepoint to track down page reference manipulation" + depends on DEBUG_KERNEL + depends on TRACEPOINTS + ---help--- + This is a feature to add tracepoint for tracking down page reference + manipulation. This tracking is useful to diagnose functional failure + due to migration failures caused by page reference mismatches. Be + careful when enabling this feature because it adds about 30 KB to the + kernel code. However the runtime performance overhead is virtually + nil until the tracepoints are actually enabled. diff --git a/mm/Makefile b/mm/Makefile index cfdd481d27a5..6da300a1414b 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -81,3 +81,4 @@ obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o obj-$(CONFIG_USERFAULTFD) += userfaultfd.o obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o +obj-$(CONFIG_DEBUG_PAGE_REF) += debug_page_ref.o diff --git a/mm/debug_page_ref.c b/mm/debug_page_ref.c new file mode 100644 index 000000000000..1aef3d562e52 --- /dev/null +++ b/mm/debug_page_ref.c @@ -0,0 +1,54 @@ +#include +#include + +#define CREATE_TRACE_POINTS +#include + +void __page_ref_set(struct page *page, int v) +{ + trace_page_ref_set(page, v); +} +EXPORT_SYMBOL(__page_ref_set); +EXPORT_TRACEPOINT_SYMBOL(page_ref_set); + +void __page_ref_mod(struct page *page, int v) +{ + trace_page_ref_mod(page, v); +} +EXPORT_SYMBOL(__page_ref_mod); +EXPORT_TRACEPOINT_SYMBOL(page_ref_mod); + +void __page_ref_mod_and_test(struct page *page, int v, int ret) +{ + trace_page_ref_mod_and_test(page, v, ret); +} +EXPORT_SYMBOL(__page_ref_mod_and_test); +EXPORT_TRACEPOINT_SYMBOL(page_ref_mod_and_test); + +void __page_ref_mod_and_return(struct page *page, int v, int ret) +{ + trace_page_ref_mod_and_return(page, v, ret); +} +EXPORT_SYMBOL(__page_ref_mod_and_return); +EXPORT_TRACEPOINT_SYMBOL(page_ref_mod_and_return); + +void __page_ref_mod_unless(struct page *page, int v, int u) +{ + trace_page_ref_mod_unless(page, v, u); +} +EXPORT_SYMBOL(__page_ref_mod_unless); +EXPORT_TRACEPOINT_SYMBOL(page_ref_mod_unless); + +void __page_ref_freeze(struct page *page, int v, int ret) +{ + trace_page_ref_freeze(page, v, ret); +} +EXPORT_SYMBOL(__page_ref_freeze); +EXPORT_TRACEPOINT_SYMBOL(page_ref_freeze); + +void __page_ref_unfreeze(struct page *page, int v) +{ + trace_page_ref_unfreeze(page, v); +} +EXPORT_SYMBOL(__page_ref_unfreeze); +EXPORT_TRACEPOINT_SYMBOL(page_ref_unfreeze); -- 2.20.1