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Message-Id: <1591243245-23052-1-git-send-email-anshuman.khandual@arm.com>
Date: Thu, 4 Jun 2020 09:30:45 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-mm@...ck.org
Cc: hughd@...gle.com, daniel.m.jordan@...cle.com, willy@...radead.org,
Anshuman Khandual <anshuman.khandual@....com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Zi Yan <ziy@...dia.com>, John Hubbard <jhubbard@...dia.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH V2] mm/vmstat: Add events for THP migration without split
Add the following new VM events which will help in validating THP migration
without split. Statistics reported through these new events will help in
performance debugging.
1. THP_MIGRATION_SUCCESS
2. THP_MIGRATION_FAILURE
THP_MIGRATION_FAILURE in particular represents an event when a THP could
not be migrated as a single entity following an allocation failure and
ended up getting split into constituent normal pages before being retried.
This event, along with PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in
quantifying and analyzing THP migration events including both success and
failure cases.
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
[hughd: fixed oops on NULL newpage]
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
Changes in V2:
- Dropped PMD reference both from code and commit message per Matthew
- Added documentation and updated the commit message per Daniel
Changes in V1: (https://patchwork.kernel.org/patch/11564497/)
- Changed function name as thp_pmd_migration_success() per John
- Folded in a fix (https://patchwork.kernel.org/patch/11563009/) from Hugh
Changes in RFC V2: (https://patchwork.kernel.org/patch/11554861/)
- Decopupled and renamed VM events from their implementation per Zi and John
- Added THP_PMD_MIGRATION_FAILURE VM event upon allocation failure and split
Changes in RFC V1: (https://patchwork.kernel.org/patch/11542055/)
Documentation/vm/page_migration.rst | 15 +++++++++++++++
include/linux/vm_event_item.h | 4 ++++
mm/migrate.c | 23 +++++++++++++++++++++++
mm/vmstat.c | 4 ++++
4 files changed, 46 insertions(+)
diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
index 1d6cd7db4e43..67e9b067fed7 100644
--- a/Documentation/vm/page_migration.rst
+++ b/Documentation/vm/page_migration.rst
@@ -253,5 +253,20 @@ which are function pointers of struct address_space_operations.
PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag
for own purpose.
+Quantifying Migration
+=====================
+Following events can be used to quantify page migration.
+
+- PGMIGRATE_SUCCESS
+- PGMIGRATE_FAIL
+- THP_MIGRATION_SUCCESS
+- THP_MIGRATION_FAILURE
+
+THP_MIGRATION_FAILURE in particular represents an event when a THP could not be
+migrated as a single entity following an allocation failure and ended up getting
+split into constituent normal pages before being retried. This event, along with
+PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in quantifying and analyzing THP
+migration events including both success and failure cases.
+
Christoph Lameter, May 8, 2006.
Minchan Kim, Mar 28, 2016.
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index ffef0f279747..6459265461df 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -91,6 +91,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
THP_ZERO_PAGE_ALLOC_FAILED,
THP_SWPOUT,
THP_SWPOUT_FALLBACK,
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ THP_MIGRATION_SUCCESS,
+ THP_MIGRATION_FAILURE,
+#endif
#endif
#ifdef CONFIG_MEMORY_BALLOON
BALLOON_INFLATE,
diff --git a/mm/migrate.c b/mm/migrate.c
index 7160c1556f79..0bb1dbb891bb 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1170,6 +1170,20 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
#define ICE_noinline
#endif
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline void thp_migration_success(bool success)
+{
+ if (success)
+ count_vm_event(THP_MIGRATION_SUCCESS);
+ else
+ count_vm_event(THP_MIGRATION_FAILURE);
+}
+#else
+static inline void thp_migration_success(bool success)
+{
+}
+#endif
+
/*
* Obtain the lock on page, remove all ptes and migrate the page
* to the newly allocated page in newpage.
@@ -1232,6 +1246,14 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
* we want to retry.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
+ /*
+ * When the page to be migrated has been freed from under
+ * us, that is considered a MIGRATEPAGE_SUCCESS, but no
+ * newpage has been allocated. It should not be counted
+ * as a successful THP migration.
+ */
+ if (newpage && PageTransHuge(newpage))
+ thp_migration_success(true);
put_page(page);
if (reason == MR_MEMORY_FAILURE) {
/*
@@ -1474,6 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
unlock_page(page);
if (!rc) {
list_safe_reset_next(page, page2, lru);
+ thp_migration_success(false);
goto retry;
}
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 96d21a792b57..4ce1ab2e9704 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1274,6 +1274,10 @@ const char * const vmstat_text[] = {
"thp_zero_page_alloc_failed",
"thp_swpout",
"thp_swpout_fallback",
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ "thp_migration_success",
+ "thp_migration_failure",
+#endif
#endif
#ifdef CONFIG_MEMORY_BALLOON
"balloon_inflate",
--
2.20.1
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