[PATCH V2 2/2] mm/migration: Add trace events for base page and HugeTLB migrations

[Anshuman Khandual <anshuman.khandual@arm.com>]

This adds two trace events for base page and HugeTLB page migrations. These
events, closely follow the implementation details like setting and removing
of PTE migration entries, which are essential operations for migration.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 include/trace/events/migrate.h | 31 +++++++++++++++++++++++++++++++
 mm/migrate.c                   |  3 +++
 mm/rmap.c                      |  5 +++++
 3 files changed, 39 insertions(+)

diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index 779f3fad9ecd..061b5128f335 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -105,6 +105,37 @@ TRACE_EVENT(mm_migrate_pages_start,
 		  __print_symbolic(__entry->reason, MIGRATE_REASON))
 );
 
+DECLARE_EVENT_CLASS(migration_pte,
+
+		TP_PROTO(unsigned long addr, unsigned long pte, int order),
+
+		TP_ARGS(addr, pte, order),
+
+		TP_STRUCT__entry(
+			__field(unsigned long, addr)
+			__field(unsigned long, pte)
+			__field(int, order)
+		),
+
+		TP_fast_assign(
+			__entry->addr = addr;
+			__entry->pte = pte;
+			__entry->order = order;
+		),
+
+		TP_printk("addr=%lx, pte=%lx order=%d", __entry->addr, __entry->pte, __entry->order)
+);
+
+DEFINE_EVENT(migration_pte, set_migration_pte,
+	TP_PROTO(unsigned long addr, unsigned long pte, int order),
+	TP_ARGS(addr, pte, order)
+);
+
+DEFINE_EVENT(migration_pte, remove_migration_pte,
+	TP_PROTO(unsigned long addr, unsigned long pte, int order),
+	TP_ARGS(addr, pte, order)
+);
+
 #endif /* _TRACE_MIGRATE_H */
 
 /* This part must be outside protection */
diff --git a/mm/migrate.c b/mm/migrate.c
index c7da064b4781..253dc5812949 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -257,6 +257,9 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
 		if (PageTransHuge(page) && PageMlocked(page))
 			clear_page_mlock(page);
 
+		trace_remove_migration_pte(pvmw.address, pte_val(pte),
+					   compound_order(new));
+
 		/* No need to invalidate - it was non-present before */
 		update_mmu_cache(vma, pvmw.address, pvmw.pte);
 	}
diff --git a/mm/rmap.c b/mm/rmap.c
index 6a1e8c7f6213..cce5dbae07f2 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -77,6 +77,7 @@
 #include <asm/tlbflush.h>
 
 #include <trace/events/tlb.h>
+#include <trace/events/migrate.h>
 
 #include "internal.h"
 
@@ -1861,6 +1862,8 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
 			if (pte_swp_uffd_wp(pteval))
 				swp_pte = pte_swp_mkuffd_wp(swp_pte);
 			set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
+			trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
+						compound_order(page));
 			/*
 			 * No need to invalidate here it will synchronize on
 			 * against the special swap migration pte.
@@ -1929,6 +1932,8 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
 			if (pte_uffd_wp(pteval))
 				swp_pte = pte_swp_mkuffd_wp(swp_pte);
 			set_pte_at(mm, address, pvmw.pte, swp_pte);
+			trace_set_migration_pte(address, pte_val(swp_pte),
+						compound_order(page));
 			/*
 			 * No need to invalidate here it will synchronize on
 			 * against the special swap migration pte.
-- 
2.20.1