Add following new vmstat events which will help in validating THP migration
without split. Statistics reported through these new VM events will help in
performance debugging.
1. THP_MIGRATION_SUCCESS
2. THP_MIGRATION_FAILURE
3. THP_MIGRATION_SPLIT
In addition, these new events also update normal page migration statistics
appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this
updates current trace event 'mm_migrate_pages' to accommodate now available
THP statistics.
Cc: Daniel Jordan <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Zi Yan <[email protected]>
Signed-off-by: Anshuman Khandual <[email protected]>
---
Changes in V3:
- Formatted new events documentation with 'fmt' tool per Matthew
- Made events universally available i.e dropped ARCH_ENABLE_THP_MIGRATION
- Added THP_MIGRATION_SPLIT
- Updated trace_mm_migrate_pages() with THP events
- Made THP events update normal page migration events as well
Changes in V2: (https://patchwork.kernel.org/patch/11586893/)
- 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 | 19 +++++++++++
include/linux/vm_event_item.h | 3 ++
include/trace/events/migrate.h | 17 ++++++++--
mm/migrate.c | 49 ++++++++++++++++++++++++++---
mm/vmstat.c | 3 ++
5 files changed, 84 insertions(+), 7 deletions(-)
diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
index 1d6cd7db4e43..e65d49f3cf86 100644
--- a/Documentation/vm/page_migration.rst
+++ b/Documentation/vm/page_migration.rst
@@ -253,5 +253,24 @@ 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.
+
+1. PGMIGRATE_SUCCESS /* Normal page migration success */
+2. PGMIGRATE_FAIL /* Normal page migration failure */
+3. THP_MIGRATION_SUCCESS /* Transparent huge page migration success */
+4. THP_MIGRATION_FAILURE /* Transparent huge page migration failure */
+5. THP_MIGRATION_SPLIT /* Transparent huge page got split, retried */
+
+THP_MIGRATION_SUCCESS is when THP is migrated successfully without getting
+split into it's subpages. THP_MIGRATION_FAILURE is when THP could neither
+be migrated nor be split. THP_MIGRATION_SPLIT is when THP could not
+just be migrated as is but instead get split into it's subpages and later
+retried as normal pages. THP events would also update normal page migration
+statistics PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. These events will help
+in quantifying and analyzing various 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 24fc7c3ae7d6..5e7ffa025589 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -95,6 +95,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
THP_ZERO_PAGE_ALLOC_FAILED,
THP_SWPOUT,
THP_SWPOUT_FALLBACK,
+ THP_MIGRATION_SUCCESS,
+ THP_MIGRATION_FAILURE,
+ THP_MIGRATION_SPLIT,
#endif
#ifdef CONFIG_MEMORY_BALLOON
BALLOON_INFLATE,
diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index 705b33d1e395..4d434398d64d 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -46,13 +46,18 @@ MIGRATE_REASON
TRACE_EVENT(mm_migrate_pages,
TP_PROTO(unsigned long succeeded, unsigned long failed,
- enum migrate_mode mode, int reason),
+ unsigned long thp_succeeded, unsigned long thp_failed,
+ unsigned long thp_split, enum migrate_mode mode, int reason),
- TP_ARGS(succeeded, failed, mode, reason),
+ TP_ARGS(succeeded, failed, thp_succeeded, thp_failed,
+ thp_split, mode, reason),
TP_STRUCT__entry(
__field( unsigned long, succeeded)
__field( unsigned long, failed)
+ __field( unsigned long, thp_succeeded)
+ __field( unsigned long, thp_failed)
+ __field( unsigned long, thp_split)
__field( enum migrate_mode, mode)
__field( int, reason)
),
@@ -60,13 +65,19 @@ TRACE_EVENT(mm_migrate_pages,
TP_fast_assign(
__entry->succeeded = succeeded;
__entry->failed = failed;
+ __entry->thp_succeeded = thp_succeeded;
+ __entry->thp_failed = thp_failed;
+ __entry->thp_split = thp_split;
__entry->mode = mode;
__entry->reason = reason;
),
- TP_printk("nr_succeeded=%lu nr_failed=%lu mode=%s reason=%s",
+ TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu mode=%s reason=%s",
__entry->succeeded,
__entry->failed,
+ __entry->thp_succeeded,
+ __entry->thp_failed,
+ __entry->thp_split,
__print_symbolic(__entry->mode, MIGRATE_MODE),
__print_symbolic(__entry->reason, MIGRATE_REASON))
);
diff --git a/mm/migrate.c b/mm/migrate.c
index f37729673558..baf3cc477d11 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1429,22 +1429,35 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
enum migrate_mode mode, int reason)
{
int retry = 1;
+ int thp_retry = 1;
int nr_failed = 0;
int nr_succeeded = 0;
+ int nr_thp_succeeded = 0;
+ int nr_thp_failed = 0;
+ int nr_thp_split = 0;
int pass = 0;
+ bool is_thp = false;
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
- int rc;
+ int rc, thp_nr_pages;
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
- for(pass = 0; pass < 10 && retry; pass++) {
+ for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
retry = 0;
+ thp_retry = 0;
list_for_each_entry_safe(page, page2, from, lru) {
retry:
+ /*
+ * THP statistics is based on the source huge page.
+ * Capture required information that might get lost
+ * during migration.
+ */
+ is_thp = PageTransHuge(page);
+ thp_nr_pages = hpage_nr_pages(page);
cond_resched();
if (PageHuge(page))
@@ -1475,15 +1488,30 @@ 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);
+ nr_thp_split++;
goto retry;
}
}
+ if (is_thp) {
+ nr_thp_failed++;
+ nr_failed += thp_nr_pages;
+ goto out;
+ }
nr_failed++;
goto out;
case -EAGAIN:
+ if (is_thp) {
+ thp_retry++;
+ break;
+ }
retry++;
break;
case MIGRATEPAGE_SUCCESS:
+ if (is_thp) {
+ nr_thp_succeeded++;
+ nr_succeeded += thp_nr_pages;
+ break;
+ }
nr_succeeded++;
break;
default:
@@ -1493,19 +1521,32 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
* removed from migration page list and not
* retried in the next outer loop.
*/
+ if (is_thp) {
+ nr_thp_failed++;
+ nr_failed += thp_nr_pages;
+ break;
+ }
nr_failed++;
break;
}
}
}
- nr_failed += retry;
+ nr_failed += retry + thp_retry;
+ nr_thp_failed += thp_retry;
rc = nr_failed;
out:
if (nr_succeeded)
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
if (nr_failed)
count_vm_events(PGMIGRATE_FAIL, nr_failed);
- trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
+ if (nr_thp_succeeded)
+ count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
+ if (nr_thp_failed)
+ count_vm_events(THP_MIGRATION_FAILURE, nr_thp_failed);
+ if (nr_thp_split)
+ count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
+ trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
+ nr_thp_failed, nr_thp_split, mode, reason);
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 3fb23a21f6dd..a0fc7c86cdb7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1280,6 +1280,9 @@ const char * const vmstat_text[] = {
"thp_zero_page_alloc_failed",
"thp_swpout",
"thp_swpout_fallback",
+ "thp_migration_success",
+ "thp_migration_failure",
+ "thp_migration_split",
#endif
#ifdef CONFIG_MEMORY_BALLOON
"balloon_inflate",
--
2.20.1
On Tue, 7 Jul 2020 05:36:55 +0530 Anshuman Khandual <[email protected]> wrote:
> Add following new vmstat events which will help in validating THP migration
> without split. Statistics reported through these new VM events will help in
> performance debugging.
>
> 1. THP_MIGRATION_SUCCESS
> 2. THP_MIGRATION_FAILURE
> 3. THP_MIGRATION_SPLIT
>
> In addition, these new events also update normal page migration statistics
> appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this
> updates current trace event 'mm_migrate_pages' to accommodate now available
> THP statistics.
Patch looks straightforward enough. It would be nice to see some
confirmation from others that these metrics are a desirable thing to
export.
> ...
>
> - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
> + if (nr_thp_succeeded)
> + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
> + if (nr_thp_failed)
> + count_vm_events(THP_MIGRATION_FAILURE, nr_thp_failed);
> + if (nr_thp_split)
> + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
Are these "if"s worthwhile to have?
> + trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
> + nr_thp_failed, nr_thp_split, mode, reason);
On 2020-07-07 13:04, Andrew Morton wrote:
> On Tue, 7 Jul 2020 05:36:55 +0530 Anshuman Khandual <[email protected]> wrote:
>
>> Add following new vmstat events which will help in validating THP migration
>> without split. Statistics reported through these new VM events will help in
>> performance debugging.
>>
>> 1. THP_MIGRATION_SUCCESS
>> 2. THP_MIGRATION_FAILURE
>> 3. THP_MIGRATION_SPLIT
>>
>> In addition, these new events also update normal page migration statistics
>> appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this
>> updates current trace event 'mm_migrate_pages' to accommodate now available
>> THP statistics.
>
> Patch looks straightforward enough. It would be nice to see some
> confirmation from others that these metrics are a desirable thing to
> export.
Taking a peek now.
>
>> ...
>>
>> - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
>> + if (nr_thp_succeeded)
>> + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
>> + if (nr_thp_failed)
>> + count_vm_events(THP_MIGRATION_FAILURE, nr_thp_failed);
>> + if (nr_thp_split)
>> + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
>
> Are these "if"s worthwhile to have?
No, they are not. And there are a couple more pre-existing cases as well,
right above what can be seen here (this patch just follows the local pattern)
that should also be removed.
thanks,
--
John Hubbard
NVIDIA
On 2020-07-06 17:06, Anshuman Khandual wrote:
> Add following new vmstat events which will help in validating THP migration
> without split. Statistics reported through these new VM events will help in
> performance debugging.
>
> 1. THP_MIGRATION_SUCCESS
> 2. THP_MIGRATION_FAILURE
> 3. THP_MIGRATION_SPLIT
>
> In addition, these new events also update normal page migration statistics
> appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this
> updates current trace event 'mm_migrate_pages' to accommodate now available
> THP statistics.
>
> Cc: Daniel Jordan <[email protected]>
> Cc: Hugh Dickins <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Zi Yan <[email protected]>
> Cc: John Hubbard <[email protected]>
> Cc: Naoya Horiguchi <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Zi Yan <[email protected]>
> Signed-off-by: Anshuman Khandual <[email protected]>
This is missing the Documentation/ Cc's, did you run scripts/get_maintainer.pl? I'm
adding linux-doc and Jonathan Corbet, for now at least. And I'll refrain from
trimming the reply.
> ---
> Changes in V3:
>
> - Formatted new events documentation with 'fmt' tool per Matthew
> - Made events universally available i.e dropped ARCH_ENABLE_THP_MIGRATION
> - Added THP_MIGRATION_SPLIT
> - Updated trace_mm_migrate_pages() with THP events
> - Made THP events update normal page migration events as well
>
> Changes in V2: (https://patchwork.kernel.org/patch/11586893/)
>
> - 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 | 19 +++++++++++
> include/linux/vm_event_item.h | 3 ++
> include/trace/events/migrate.h | 17 ++++++++--
> mm/migrate.c | 49 ++++++++++++++++++++++++++---
> mm/vmstat.c | 3 ++
> 5 files changed, 84 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
> index 1d6cd7db4e43..e65d49f3cf86 100644
> --- a/Documentation/vm/page_migration.rst
> +++ b/Documentation/vm/page_migration.rst
> @@ -253,5 +253,24 @@ 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.
> +
> +1. PGMIGRATE_SUCCESS /* Normal page migration success */
This doesn't explain what's going on with the new combined counter
behavior. See the proposal below.
> +2. PGMIGRATE_FAIL /* Normal page migration failure */
> +3. THP_MIGRATION_SUCCESS /* Transparent huge page migration success */
> +4. THP_MIGRATION_FAILURE /* Transparent huge page migration failure */
Shouldn't that be THP_MIGRATION_FAIL, in order to match the existing naming
scheme here?
> +5. THP_MIGRATION_SPLIT /* Transparent huge page got split, retried */
> +
> +THP_MIGRATION_SUCCESS is when THP is migrated successfully without getting
> +split into it's subpages. THP_MIGRATION_FAILURE is when THP could neither
> +be migrated nor be split. THP_MIGRATION_SPLIT is when THP could not
> +just be migrated as is but instead get split into it's subpages and later
> +retried as normal pages. THP events would also update normal page migration
> +statistics PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. These events will help
> +in quantifying and analyzing various THP migration events including both
> +success and failure cases.
> +
I would like to propose the following instead of the above. It's rewritten
so as to add explanations for the new behavior, remove the redundancy (the last
sentence in particular is a justification, and belongs in a commit log if anywhere,
not in the doc itself), fix a few typos, use the full 80 columns, and clarify a
bit as well. It uses the new THP_MIGRATION_FAIL name:
Monitoring Migration
=====================
The following events (counters) can be used to monitor page migration.
1. PGMIGRATE_SUCCESS: Normal page migration success. Each count means that a
page was migrated. If the page was a non-THP page, then this counter is
increased by one. If the page was a THP, then this counter is increased by
the number of THP subpages. For example, migration of a single 2MB THP that
has 4KB-size base pages (subpages) will cause this counter to increase by
512.
2. PGMIGRATE_FAIL: Normal page migration failure. Same counting rules as for
_SUCCESS, above: this will be increased by the number of subpages, if it was
a THP.
3. THP_MIGRATION_SUCCESS: A THP was migrated without being split.
4. THP_MIGRATION_FAIL: A THP could not be migrated at all, even after being
split.
5. THP_MIGRATION_SPLIT: A THP was migrated, but not as such: first, the THP had
to be split. After splitting, a migration retry was used for the sub-pages,
and that retry succeeded.
THP_MIGRATION_* events also update the appropriate PGMIGRATE_SUCCESS or
PGMIGRATE_FAILURE events. For example, a THP migration failure will cause both
THP_MIGRATION_FAIL and PGMIGRATE_FAIL to increase.
> 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 24fc7c3ae7d6..5e7ffa025589 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -95,6 +95,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> THP_ZERO_PAGE_ALLOC_FAILED,
> THP_SWPOUT,
> THP_SWPOUT_FALLBACK,
> + THP_MIGRATION_SUCCESS,
> + THP_MIGRATION_FAILURE,
> + THP_MIGRATION_SPLIT,
> #endif
> #ifdef CONFIG_MEMORY_BALLOON
> BALLOON_INFLATE,
> diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
> index 705b33d1e395..4d434398d64d 100644
> --- a/include/trace/events/migrate.h
> +++ b/include/trace/events/migrate.h
> @@ -46,13 +46,18 @@ MIGRATE_REASON
> TRACE_EVENT(mm_migrate_pages,
>
> TP_PROTO(unsigned long succeeded, unsigned long failed,
> - enum migrate_mode mode, int reason),
> + unsigned long thp_succeeded, unsigned long thp_failed,
> + unsigned long thp_split, enum migrate_mode mode, int reason),
>
> - TP_ARGS(succeeded, failed, mode, reason),
> + TP_ARGS(succeeded, failed, thp_succeeded, thp_failed,
> + thp_split, mode, reason),
>
> TP_STRUCT__entry(
> __field( unsigned long, succeeded)
> __field( unsigned long, failed)
> + __field( unsigned long, thp_succeeded)
> + __field( unsigned long, thp_failed)
> + __field( unsigned long, thp_split)
> __field( enum migrate_mode, mode)
> __field( int, reason)
> ),
> @@ -60,13 +65,19 @@ TRACE_EVENT(mm_migrate_pages,
> TP_fast_assign(
> __entry->succeeded = succeeded;
> __entry->failed = failed;
> + __entry->thp_succeeded = thp_succeeded;
> + __entry->thp_failed = thp_failed;
> + __entry->thp_split = thp_split;
> __entry->mode = mode;
> __entry->reason = reason;
> ),
>
> - TP_printk("nr_succeeded=%lu nr_failed=%lu mode=%s reason=%s",
> + TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu mode=%s reason=%s",
> __entry->succeeded,
> __entry->failed,
> + __entry->thp_succeeded,
> + __entry->thp_failed,
> + __entry->thp_split,
> __print_symbolic(__entry->mode, MIGRATE_MODE),
> __print_symbolic(__entry->reason, MIGRATE_REASON))
> );
> diff --git a/mm/migrate.c b/mm/migrate.c
> index f37729673558..baf3cc477d11 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1429,22 +1429,35 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> enum migrate_mode mode, int reason)
> {
> int retry = 1;
> + int thp_retry = 1;
> int nr_failed = 0;
> int nr_succeeded = 0;
> + int nr_thp_succeeded = 0;
> + int nr_thp_failed = 0;
> + int nr_thp_split = 0;
> int pass = 0;
> + bool is_thp = false;
> struct page *page;
> struct page *page2;
> int swapwrite = current->flags & PF_SWAPWRITE;
> - int rc;
> + int rc, thp_nr_pages;
>
> if (!swapwrite)
> current->flags |= PF_SWAPWRITE;
>
> - for(pass = 0; pass < 10 && retry; pass++) {
> + for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
> retry = 0;
> + thp_retry = 0;
>
> list_for_each_entry_safe(page, page2, from, lru) {
> retry:
> + /*
> + * THP statistics is based on the source huge page.
> + * Capture required information that might get lost
> + * during migration.
> + */
> + is_thp = PageTransHuge(page);
> + thp_nr_pages = hpage_nr_pages(page);
> cond_resched();
>
> if (PageHuge(page))
> @@ -1475,15 +1488,30 @@ 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);
> + nr_thp_split++;
> goto retry;
> }
> }
> + if (is_thp) {
> + nr_thp_failed++;
> + nr_failed += thp_nr_pages;
> + goto out;
> + }
> nr_failed++;
> goto out;
> case -EAGAIN:
> + if (is_thp) {
> + thp_retry++;
> + break;
> + }
> retry++;
> break;
> case MIGRATEPAGE_SUCCESS:
> + if (is_thp) {
> + nr_thp_succeeded++;
> + nr_succeeded += thp_nr_pages;
> + break;
> + }
> nr_succeeded++;
> break;
> default:
> @@ -1493,19 +1521,32 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> * removed from migration page list and not
> * retried in the next outer loop.
> */
> + if (is_thp) {
> + nr_thp_failed++;
> + nr_failed += thp_nr_pages;
> + break;
> + }
> nr_failed++;
> break;
> }
> }
> }
> - nr_failed += retry;
> + nr_failed += retry + thp_retry;
> + nr_thp_failed += thp_retry;
> rc = nr_failed;
> out:
> if (nr_succeeded)
> count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
> if (nr_failed)
> count_vm_events(PGMIGRATE_FAIL, nr_failed);
> - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
> + if (nr_thp_succeeded)
> + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
> + if (nr_thp_failed)
> + count_vm_events(THP_MIGRATION_FAILURE, nr_thp_failed);
> + if (nr_thp_split)
> + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
As mentioned in the other thread, those "ifs" should be removed. I think you
can also get away with removing the two pre-existing "ifs" in the same
patch, too, just to keep the whole set consistent and more readable.
> + trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
> + nr_thp_failed, nr_thp_split, mode, reason);
>
> if (!swapwrite)
> current->flags &= ~PF_SWAPWRITE;
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 3fb23a21f6dd..a0fc7c86cdb7 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1280,6 +1280,9 @@ const char * const vmstat_text[] = {
> "thp_zero_page_alloc_failed",
> "thp_swpout",
> "thp_swpout_fallback",
> + "thp_migration_success",
> + "thp_migration_failure",
> + "thp_migration_split",
> #endif
> #ifdef CONFIG_MEMORY_BALLOON
> "balloon_inflate",
>
thanks,
--
John Hubbard
NVIDIA
On 07/08/2020 05:31 AM, John Hubbard wrote:
> On 2020-07-06 17:06, Anshuman Khandual wrote:
>> Add following new vmstat events which will help in validating THP migration
>> without split. Statistics reported through these new VM events will help in
>> performance debugging.
>>
>> 1. THP_MIGRATION_SUCCESS
>> 2. THP_MIGRATION_FAILURE
>> 3. THP_MIGRATION_SPLIT
>>
>> In addition, these new events also update normal page migration statistics
>> appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this
>> updates current trace event 'mm_migrate_pages' to accommodate now available
>> THP statistics.
>>
>> Cc: Daniel Jordan <[email protected]>
>> Cc: Hugh Dickins <[email protected]>
>> Cc: Matthew Wilcox <[email protected]>
>> Cc: Zi Yan <[email protected]>
>> Cc: John Hubbard <[email protected]>
>> Cc: Naoya Horiguchi <[email protected]>
>> Cc: Andrew Morton <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Signed-off-by: Zi Yan <[email protected]>
>> Signed-off-by: Anshuman Khandual <[email protected]>
>
>
> This is missing the Documentation/ Cc's, did you run scripts/get_maintainer.pl? I'm
> adding linux-doc and Jonathan Corbet, for now at least. And I'll refrain from
> trimming the reply.
I had missed the Documention/ Cc's, thanks for adding them here. Will
update the Cc list next time around.
>
>
>> ---
>> Changes in V3:
>>
>> - Formatted new events documentation with 'fmt' tool per Matthew
>> - Made events universally available i.e dropped ARCH_ENABLE_THP_MIGRATION
>> - Added THP_MIGRATION_SPLIT
>> - Updated trace_mm_migrate_pages() with THP events
>> - Made THP events update normal page migration events as well
>>
>> Changes in V2: (https://patchwork.kernel.org/patch/11586893/)
>>
>> - 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 | 19 +++++++++++
>> include/linux/vm_event_item.h | 3 ++
>> include/trace/events/migrate.h | 17 ++++++++--
>> mm/migrate.c | 49 ++++++++++++++++++++++++++---
>> mm/vmstat.c | 3 ++
>> 5 files changed, 84 insertions(+), 7 deletions(-)
>>
>> diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
>> index 1d6cd7db4e43..e65d49f3cf86 100644
>> --- a/Documentation/vm/page_migration.rst
>> +++ b/Documentation/vm/page_migration.rst
>> @@ -253,5 +253,24 @@ 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.
>> +
>> +1. PGMIGRATE_SUCCESS /* Normal page migration success */
>
>
> This doesn't explain what's going on with the new combined counter
> behavior. See the proposal below.
>
>
>> +2. PGMIGRATE_FAIL /* Normal page migration failure */
>> +3. THP_MIGRATION_SUCCESS /* Transparent huge page migration success */
>> +4. THP_MIGRATION_FAILURE /* Transparent huge page migration failure */
>
>
> Shouldn't that be THP_MIGRATION_FAIL, in order to match the existing naming
> scheme here?
Sure, will change it.
>
>
>> +5. THP_MIGRATION_SPLIT /* Transparent huge page got split, retried */
>> +
>> +THP_MIGRATION_SUCCESS is when THP is migrated successfully without getting
>> +split into it's subpages. THP_MIGRATION_FAILURE is when THP could neither
>> +be migrated nor be split. THP_MIGRATION_SPLIT is when THP could not
>> +just be migrated as is but instead get split into it's subpages and later
>> +retried as normal pages. THP events would also update normal page migration
>> +statistics PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. These events will help
>> +in quantifying and analyzing various THP migration events including both
>> +success and failure cases.
>> +
>
>
> I would like to propose the following instead of the above. It's rewritten
> so as to add explanations for the new behavior, remove the redundancy (the last
> sentence in particular is a justification, and belongs in a commit log if anywhere,
> not in the doc itself), fix a few typos, use the full 80 columns, and clarify a
> bit as well. It uses the new THP_MIGRATION_FAIL name:
>
>
> Monitoring Migration
> =====================
>
> The following events (counters) can be used to monitor page migration.
>
> 1. PGMIGRATE_SUCCESS: Normal page migration success. Each count means that a
> page was migrated. If the page was a non-THP page, then this counter is
> increased by one. If the page was a THP, then this counter is increased by
> the number of THP subpages. For example, migration of a single 2MB THP that
> has 4KB-size base pages (subpages) will cause this counter to increase by
> 512.
>
> 2. PGMIGRATE_FAIL: Normal page migration failure. Same counting rules as for
> _SUCCESS, above: this will be increased by the number of subpages, if it was
> a THP.
>
> 3. THP_MIGRATION_SUCCESS: A THP was migrated without being split.
>
> 4. THP_MIGRATION_FAIL: A THP could not be migrated at all, even after being
> split.
>
> 5. THP_MIGRATION_SPLIT: A THP was migrated, but not as such: first, the THP had
> to be split. After splitting, a migration retry was used for the sub-pages,
> and that retry succeeded.
The last part might not be true. All that THP_MIGRATION_SPLIT tracks is whether
the THP was split or not. Whether it's subpages got successfully migrated later
or not, would be hidden in overall PGMIGRATE_SUCCESS and PGMIGRATE_FAIL values.
>
> THP_MIGRATION_* events also update the appropriate PGMIGRATE_SUCCESS or
> PGMIGRATE_FAILURE events. For example, a THP migration failure will cause both
> THP_MIGRATION_FAIL and PGMIGRATE_FAIL to increase.
Above explanation (probably with some changes) looks better, will update.
>
>
>> 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 24fc7c3ae7d6..5e7ffa025589 100644
>> --- a/include/linux/vm_event_item.h
>> +++ b/include/linux/vm_event_item.h
>> @@ -95,6 +95,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>> THP_ZERO_PAGE_ALLOC_FAILED,
>> THP_SWPOUT,
>> THP_SWPOUT_FALLBACK,
>> + THP_MIGRATION_SUCCESS,
>> + THP_MIGRATION_FAILURE,
>> + THP_MIGRATION_SPLIT,
>> #endif
>> #ifdef CONFIG_MEMORY_BALLOON
>> BALLOON_INFLATE,
>> diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
>> index 705b33d1e395..4d434398d64d 100644
>> --- a/include/trace/events/migrate.h
>> +++ b/include/trace/events/migrate.h
>> @@ -46,13 +46,18 @@ MIGRATE_REASON
>> TRACE_EVENT(mm_migrate_pages,
>> TP_PROTO(unsigned long succeeded, unsigned long failed,
>> - enum migrate_mode mode, int reason),
>> + unsigned long thp_succeeded, unsigned long thp_failed,
>> + unsigned long thp_split, enum migrate_mode mode, int reason),
>> - TP_ARGS(succeeded, failed, mode, reason),
>> + TP_ARGS(succeeded, failed, thp_succeeded, thp_failed,
>> + thp_split, mode, reason),
>> TP_STRUCT__entry(
>> __field( unsigned long, succeeded)
>> __field( unsigned long, failed)
>> + __field( unsigned long, thp_succeeded)
>> + __field( unsigned long, thp_failed)
>> + __field( unsigned long, thp_split)
>> __field( enum migrate_mode, mode)
>> __field( int, reason)
>> ),
>> @@ -60,13 +65,19 @@ TRACE_EVENT(mm_migrate_pages,
>> TP_fast_assign(
>> __entry->succeeded = succeeded;
>> __entry->failed = failed;
>> + __entry->thp_succeeded = thp_succeeded;
>> + __entry->thp_failed = thp_failed;
>> + __entry->thp_split = thp_split;
>> __entry->mode = mode;
>> __entry->reason = reason;
>> ),
>> - TP_printk("nr_succeeded=%lu nr_failed=%lu mode=%s reason=%s",
>> + TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu mode=%s reason=%s",
>> __entry->succeeded,
>> __entry->failed,
>> + __entry->thp_succeeded,
>> + __entry->thp_failed,
>> + __entry->thp_split,
>> __print_symbolic(__entry->mode, MIGRATE_MODE),
>> __print_symbolic(__entry->reason, MIGRATE_REASON))
>> );
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index f37729673558..baf3cc477d11 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1429,22 +1429,35 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> enum migrate_mode mode, int reason)
>> {
>> int retry = 1;
>> + int thp_retry = 1;
>> int nr_failed = 0;
>> int nr_succeeded = 0;
>> + int nr_thp_succeeded = 0;
>> + int nr_thp_failed = 0;
>> + int nr_thp_split = 0;
>> int pass = 0;
>> + bool is_thp = false;
>> struct page *page;
>> struct page *page2;
>> int swapwrite = current->flags & PF_SWAPWRITE;
>> - int rc;
>> + int rc, thp_nr_pages;
>> if (!swapwrite)
>> current->flags |= PF_SWAPWRITE;
>> - for(pass = 0; pass < 10 && retry; pass++) {
>> + for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
>> retry = 0;
>> + thp_retry = 0;
>> list_for_each_entry_safe(page, page2, from, lru) {
>> retry:
>> + /*
>> + * THP statistics is based on the source huge page.
>> + * Capture required information that might get lost
>> + * during migration.
>> + */
>> + is_thp = PageTransHuge(page);
>> + thp_nr_pages = hpage_nr_pages(page);
>> cond_resched();
>> if (PageHuge(page))
>> @@ -1475,15 +1488,30 @@ 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);
>> + nr_thp_split++;
>> goto retry;
>> }
>> }
>> + if (is_thp) {
>> + nr_thp_failed++;
>> + nr_failed += thp_nr_pages;
>> + goto out;
>> + }
>> nr_failed++;
>> goto out;
>> case -EAGAIN:
>> + if (is_thp) {
>> + thp_retry++;
>> + break;
>> + }
>> retry++;
>> break;
>> case MIGRATEPAGE_SUCCESS:
>> + if (is_thp) {
>> + nr_thp_succeeded++;
>> + nr_succeeded += thp_nr_pages;
>> + break;
>> + }
>> nr_succeeded++;
>> break;
>> default:
>> @@ -1493,19 +1521,32 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> * removed from migration page list and not
>> * retried in the next outer loop.
>> */
>> + if (is_thp) {
>> + nr_thp_failed++;
>> + nr_failed += thp_nr_pages;
>> + break;
>> + }
>> nr_failed++;
>> break;
>> }
>> }
>> }
>> - nr_failed += retry;
>> + nr_failed += retry + thp_retry;
>> + nr_thp_failed += thp_retry;
>> rc = nr_failed;
>> out:
>> if (nr_succeeded)
>> count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
>> if (nr_failed)
>> count_vm_events(PGMIGRATE_FAIL, nr_failed);
>> - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
>> + if (nr_thp_succeeded)
>> + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
>> + if (nr_thp_failed)
>> + count_vm_events(THP_MIGRATION_FAILURE, nr_thp_failed);
>> + if (nr_thp_split)
>> + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
>
> As mentioned in the other thread, those "ifs" should be removed. I think you
> can also get away with removing the two pre-existing "ifs" in the same
> patch, too, just to keep the whole set consistent and more readable.
Makes sense, will do.