[PATCH v3] mm: vmscan: rework lru_shrink and write_folio tracepoints

[PATCH v3] mm: vmscan: rework lru_shrink and write_folio tracepoints

[qiwu.chen(陈启武)]

From: "qiwu.chen" <qiwu.chen@transsion.com>

Currently, reclaim_flags always contains RECLAIM_WB_ASYNC in lru_shrink
tracepoints since commit 41ac1999c3e35 ("mm: vmscan: do not stall on
writeback during memory compaction"), which is useless for debugging
memory pressure issues. Other RECLAIM_WB_* flags are not used anywhere
else, so they can be directly removed.
This patch reworks the lru_shrink and write_folio tracepoints for better
correlation and analysis:
 - traces each folio lru type instead of reclaim_flags.
 - traces each lru_shrink with reason.
 - remove the printing of the unnecessary PFN for mm_vmscan_write_folio.
 - traces the number of activated folios by folio_check_references.

Fixes: 41ac1999c3e35 ("mm: vmscan: do not stall on writeback during memory compaction")
Signed-off-by: qiwu.chen <qiwu.chen@transsion.com>
---
 include/linux/vmstat.h        |  1 +
 include/trace/events/vmscan.h | 77 ++++++++++++++++-------------------
 mm/vmscan.c                   | 11 ++---
 3 files changed, 41 insertions(+), 48 deletions(-)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 5b31d8e7ae40..72c3b51a633f 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -22,6 +22,7 @@ struct reclaim_stat {
 	unsigned nr_immediate;
 	unsigned nr_activate[ANON_AND_FILE];
 	unsigned nr_ref_keep;
+	unsigned nr_ref_activate;
 	unsigned nr_unmap_fail;
 	unsigned nr_lazyfree_fail;
 	unsigned nr_demoted;
diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index b4bf7b8def1f..66fa5bf9a439 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -11,22 +11,6 @@
 #include <linux/memcontrol.h>
 #include <trace/events/mmflags.h>
 
-#define RECLAIM_WB_ANON		0x0001u
-#define RECLAIM_WB_FILE		0x0002u
-#define RECLAIM_WB_MIXED	0x0010u
-#define RECLAIM_WB_SYNC		0x0004u /* Unused, all reclaim async */
-#define RECLAIM_WB_ASYNC	0x0008u
-#define RECLAIM_WB_LRU		(RECLAIM_WB_ANON|RECLAIM_WB_FILE)
-
-#define show_reclaim_flags(flags)				\
-	(flags) ? __print_flags(flags, "|",			\
-		{RECLAIM_WB_ANON,	"RECLAIM_WB_ANON"},	\
-		{RECLAIM_WB_FILE,	"RECLAIM_WB_FILE"},	\
-		{RECLAIM_WB_MIXED,	"RECLAIM_WB_MIXED"},	\
-		{RECLAIM_WB_SYNC,	"RECLAIM_WB_SYNC"},	\
-		{RECLAIM_WB_ASYNC,	"RECLAIM_WB_ASYNC"}	\
-		) : "RECLAIM_WB_NONE"
-
 #define _VMSCAN_THROTTLE_WRITEBACK	(1 << VMSCAN_THROTTLE_WRITEBACK)
 #define _VMSCAN_THROTTLE_ISOLATED	(1 << VMSCAN_THROTTLE_ISOLATED)
 #define _VMSCAN_THROTTLE_NOPROGRESS	(1 << VMSCAN_THROTTLE_NOPROGRESS)
@@ -51,10 +35,11 @@ TRACE_DEFINE_ENUM(KSWAPD_CLEAR_HOPELESS_PCP);
 	{KSWAPD_CLEAR_HOPELESS_PCP,	"PCP"},		\
 	{KSWAPD_CLEAR_HOPELESS_OTHER,	"OTHER"}
 
-#define trace_reclaim_flags(file) ( \
-	(file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
-	(RECLAIM_WB_ASYNC) \
-	)
+#define trace_reclaim_reason_ops		\
+	{PGSTEAL_KSWAPD,	"KSWAPD"},	\
+	{PGSTEAL_DIRECT,	"DIRECT"},	\
+	{PGSTEAL_KHUGEPAGED,	"KHUGEPAGED"}, \
+	{PGSTEAL_PROACTIVE,	"PROACTIVE"}
 
 TRACE_EVENT(mm_vmscan_kswapd_sleep,
 
@@ -413,20 +398,18 @@ TRACE_EVENT(mm_vmscan_write_folio,
 	TP_ARGS(folio),
 
 	TP_STRUCT__entry(
-		__field(unsigned long, pfn)
-		__field(int, reclaim_flags)
+		__field(struct folio *, folio)
+		__field(int, lru)
 	),
 
 	TP_fast_assign(
-		__entry->pfn = folio_pfn(folio);
-		__entry->reclaim_flags = trace_reclaim_flags(
-						folio_is_file_lru(folio));
+		__entry->folio = folio;
+		__entry->lru = folio_lru_list(folio);
 	),
 
-	TP_printk("page=%p pfn=0x%lx flags=%s",
-		pfn_to_page(__entry->pfn),
-		__entry->pfn,
-		show_reclaim_flags(__entry->reclaim_flags))
+	TP_printk("folio=%p lru=%s",
+		__entry->folio,
+		__print_symbolic(__entry->lru, LRU_NAMES))
 );
 
 TRACE_EVENT(mm_vmscan_reclaim_pages,
@@ -478,9 +461,9 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
 
 	TP_PROTO(int nid,
 		unsigned long nr_scanned, unsigned long nr_reclaimed,
-		struct reclaim_stat *stat, int priority, int file),
+		struct reclaim_stat *stat, int priority, int lru, int reason),
 
-	TP_ARGS(nid, nr_scanned, nr_reclaimed, stat, priority, file),
+	TP_ARGS(nid, nr_scanned, nr_reclaimed, stat, priority, lru, reason),
 
 	TP_STRUCT__entry(
 		__field(int, nid)
@@ -493,9 +476,11 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
 		__field(unsigned int, nr_activate0)
 		__field(unsigned int, nr_activate1)
 		__field(unsigned long, nr_ref_keep)
+		__field(unsigned long, nr_ref_activate)
 		__field(unsigned long, nr_unmap_fail)
 		__field(int, priority)
-		__field(int, reclaim_flags)
+		__field(int, lru)
+		__field(int, reason)
 	),
 
 	TP_fast_assign(
@@ -509,29 +494,32 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
 		__entry->nr_activate0 = stat->nr_activate[0];
 		__entry->nr_activate1 = stat->nr_activate[1];
 		__entry->nr_ref_keep = stat->nr_ref_keep;
+		__entry->nr_ref_activate = stat->nr_ref_activate;
 		__entry->nr_unmap_fail = stat->nr_unmap_fail;
 		__entry->priority = priority;
-		__entry->reclaim_flags = trace_reclaim_flags(file);
+		__entry->lru = lru;
+		__entry->reason = reason;
 	),
 
-	TP_printk("nid=%d nr_scanned=%ld nr_reclaimed=%ld nr_dirty=%ld nr_writeback=%ld nr_congested=%ld nr_immediate=%ld nr_activate_anon=%d nr_activate_file=%d nr_ref_keep=%ld nr_unmap_fail=%ld priority=%d flags=%s",
+	TP_printk("nid=%d nr_scanned=%ld nr_reclaimed=%ld nr_dirty=%ld nr_writeback=%ld nr_congested=%ld nr_immediate=%ld nr_activate_anon=%d nr_activate_file=%d nr_ref_keep=%ld nr_ref_activate=%ld nr_unmap_fail=%ld priority=%d lru=%s reason=%s",
 		__entry->nid,
 		__entry->nr_scanned, __entry->nr_reclaimed,
 		__entry->nr_dirty, __entry->nr_writeback,
 		__entry->nr_congested, __entry->nr_immediate,
 		__entry->nr_activate0, __entry->nr_activate1,
-		__entry->nr_ref_keep, __entry->nr_unmap_fail,
-		__entry->priority,
-		show_reclaim_flags(__entry->reclaim_flags))
+		__entry->nr_ref_keep, __entry->nr_ref_keep,
+		__entry->nr_unmap_fail, __entry->priority,
+		__print_symbolic(__entry->lru, LRU_NAMES),
+		__print_symbolic(__entry->reason, trace_reclaim_reason_ops))
 );
 
 TRACE_EVENT(mm_vmscan_lru_shrink_active,
 
 	TP_PROTO(int nid, unsigned long nr_taken,
 		unsigned long nr_active, unsigned long nr_deactivated,
-		unsigned long nr_referenced, int priority, int file),
+		unsigned long nr_referenced, int priority, int lru, int reason),
 
-	TP_ARGS(nid, nr_taken, nr_active, nr_deactivated, nr_referenced, priority, file),
+	TP_ARGS(nid, nr_taken, nr_active, nr_deactivated, nr_referenced, priority, lru, reason),
 
 	TP_STRUCT__entry(
 		__field(int, nid)
@@ -540,7 +528,8 @@ TRACE_EVENT(mm_vmscan_lru_shrink_active,
 		__field(unsigned long, nr_deactivated)
 		__field(unsigned long, nr_referenced)
 		__field(int, priority)
-		__field(int, reclaim_flags)
+		__field(int, lru)
+		__field(int, reason)
 	),
 
 	TP_fast_assign(
@@ -550,15 +539,17 @@ TRACE_EVENT(mm_vmscan_lru_shrink_active,
 		__entry->nr_deactivated = nr_deactivated;
 		__entry->nr_referenced = nr_referenced;
 		__entry->priority = priority;
-		__entry->reclaim_flags = trace_reclaim_flags(file);
+		__entry->lru = lru;
+		__entry->reason = reason;
 	),
 
-	TP_printk("nid=%d nr_taken=%ld nr_active=%ld nr_deactivated=%ld nr_referenced=%ld priority=%d flags=%s",
+	TP_printk("nid=%d nr_taken=%ld nr_active=%ld nr_deactivated=%ld nr_referenced=%ld priority=%d lru=%s reason=%s",
 		__entry->nid,
 		__entry->nr_taken,
 		__entry->nr_active, __entry->nr_deactivated, __entry->nr_referenced,
 		__entry->priority,
-		show_reclaim_flags(__entry->reclaim_flags))
+		__print_symbolic(__entry->lru, LRU_NAMES),
+		__print_symbolic(__entry->reason, trace_reclaim_reason_ops))
 );
 
 TRACE_EVENT(mm_vmscan_node_reclaim_begin,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f11491ee9ed5..c90e2dc1d324 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1233,6 +1233,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 
 		switch (references) {
 		case FOLIOREF_ACTIVATE:
+			stat->nr_ref_activate += nr_pages;
 			goto activate_locked;
 		case FOLIOREF_KEEP:
 			stat->nr_ref_keep += nr_pages;
@@ -2041,7 +2042,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
 
 	handle_reclaim_writeback(nr_taken, pgdat, sc, &stat);
 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
-			nr_scanned, nr_reclaimed, &stat, sc->priority, file);
+			nr_scanned, nr_reclaimed, &stat, sc->priority, lru, item);
 	return nr_reclaimed;
 }
 
@@ -2148,7 +2149,8 @@ static void shrink_active_list(unsigned long nr_to_scan,
 		mod_lruvec_state(lruvec, PGROTATE_ANON + file, nr_rotated);
 
 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
-			nr_deactivate, nr_rotated, sc->priority, file);
+			nr_deactivate, nr_rotated, sc->priority, lru,
+			PGSTEAL_KSWAPD + reclaimer_offset(sc));
 }
 
 static unsigned int reclaim_folio_list(struct list_head *folio_list,
@@ -4910,12 +4912,13 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 	reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false, memcg);
 	sc->nr_reclaimed += reclaimed;
 	total_reclaimed += reclaimed;
+	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
 	/* Retry pass is only meant for clean folios without new isolation */
 	if (isolated)
 		handle_reclaim_writeback(isolated, pgdat, sc, &stat);
 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
 			type_scanned, reclaimed, &stat, sc->priority,
-			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
+			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON, item);
 
 	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
 		DEFINE_MIN_SEQ(lruvec);
@@ -4946,8 +4949,6 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(sc),
 					stat.nr_demoted);
-
-	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
 	mod_lruvec_state(lruvec, item, reclaimed);
 	mod_lruvec_state(lruvec, PGSTEAL_ANON + type, reclaimed);
 
-- 
2.50.1

Re: [PATCH v3] mm: vmscan: rework lru_shrink and write_folio tracepoints

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [Medium] The `mm_vmscan_lru_shrink_inactive` tracepoint prints `nr_ref_keep` twice and omits the newly added `nr_ref_activate` field.
- [Medium] Missing TRACE_DEFINE_ENUM exports for PGSTEAL_* enum values used in trace_reclaim_reason_ops.
- [Medium] The patch breaks the in-tree `trace-vmscan-postprocess.pl` script by altering tracepoint arguments without updating the script.
--

commit 415a9b2c51b867b9381070883253c78fbde68aee
Author: qiwu.chen <qiwu.chen@transsion.com>

mm: vmscan: rework lru_shrink and write_folio tracepoints

This commit reworks the lru_shrink and write_folio tracepoints for better
correlation and analysis. It traces each folio LRU type and reclaim reason,
adds activation statistics, and removes some unused reclaim flags.

> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index 8a872990b4bee..db6c6d2d777af 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
[ ... ]
> -#define trace_reclaim_flags(file) ( \
> -	(file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
> -	(RECLAIM_WB_ASYNC) \
> -	)
> +#define trace_reclaim_reason_ops		\
> +	{PGSTEAL_KSWAPD,	"KSWAPD"},	\
> +	{PGSTEAL_DIRECT,	"DIRECT"},	\
> +	{PGSTEAL_KHUGEPAGED,	"KHUGEPAGED"}, \
> +	{PGSTEAL_PROACTIVE,	"PROACTIVE"}

[Severity: Medium]
Since this macro maps enums to strings for use with __print_symbolic(), do
these enum values need corresponding TRACE_DEFINE_ENUM() exports?

Without them, userspace tools like perf or trace-cmd will not be able to
evaluate the enum values from the trace format file and will fail to parse
the reason field.

[ ... ]
> @@ -495,29 +480,32 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
>  		__entry->nr_activate0 = stat->nr_activate[0];
>  		__entry->nr_activate1 = stat->nr_activate[1];
>  		__entry->nr_ref_keep = stat->nr_ref_keep;
> +		__entry->nr_ref_activate = stat->nr_ref_activate;
>  		__entry->nr_unmap_fail = stat->nr_unmap_fail;
>  		__entry->priority = priority;
> -		__entry->reclaim_flags = trace_reclaim_flags(file);
> +		__entry->lru = lru;
> +		__entry->reason = reason;
>  	),
>  
> -	TP_printk("nid=%d nr_scanned=%ld nr_reclaimed=%ld nr_dirty=%ld nr_writeback=%ld nr_congested=%ld nr_immediate=%ld nr_activate_anon=%d nr_activate_file=%d nr_ref_keep=%ld nr_unmap_fail=%ld priority=%d flags=%s",
> +	TP_printk("nid=%d nr_scanned=%ld nr_reclaimed=%ld nr_dirty=%ld nr_writeback=%ld nr_congested=%ld nr_immediate=%ld nr_activate_anon=%d nr_activate_file=%d nr_ref_keep=%ld nr_ref_activate=%ld nr_unmap_fail=%ld priority=%d lru=%s reason=%s",
>  		__entry->nid,
>  		__entry->nr_scanned, __entry->nr_reclaimed,
>  		__entry->nr_dirty, __entry->nr_writeback,
>  		__entry->nr_congested, __entry->nr_immediate,
>  		__entry->nr_activate0, __entry->nr_activate1,
> -		__entry->nr_ref_keep, __entry->nr_unmap_fail,
> -		__entry->priority,
> -		show_reclaim_flags(__entry->reclaim_flags))
> +		__entry->nr_ref_keep, __entry->nr_ref_keep,

[Severity: Medium]
Is the second __entry->nr_ref_keep here a typo?

It looks like it should be __entry->nr_ref_activate to match the format
string. The duplicated nr_ref_keep argument causes the correct
nr_ref_activate field to be ignored in the trace output.

[Severity: Medium]
Does the Documentation/trace/postprocess/trace-vmscan-postprocess.pl
script also need to be updated to handle this new format?

The script contains a hardcoded regular expression for this tracepoint:

$regex_lru_shrink_inactive = generate_traceevent_regex(
		"vmscan/mm_vmscan_lru_shrink_inactive",
		$regex_lru_shrink_inactive_default,
		"nid", "nr_scanned", "nr_reclaimed", "nr_dirty", "nr_writeback",
		"nr_congested", "nr_immediate", "nr_activate_anon",
		"nr_activate_file", "nr_ref_keep",
		"nr_unmap_fail", "priority", "flags");

Since flags was renamed to lru, and reason and nr_ref_activate were
added, the parsing logic in the script will fail on traces using this new
format.

> +		__entry->nr_unmap_fail, __entry->priority,
> +		__print_symbolic(__entry->lru, LRU_NAMES),
> +		__print_symbolic(__entry->reason, trace_reclaim_reason_ops))
>  );

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260914072433.39636-1-qiwu.chen@transsion.com?part=1

Re: [PATCH v3] mm: vmscan: rework lru_shrink and write_folio tracepoints

[Matthew Wilcox]

On Mon, Sep 14, 2026 at 07:24:37AM +0000, qiwu.chen(陈启武) wrote:
>  
> -	TP_printk("page=%p pfn=0x%lx flags=%s",
> -		pfn_to_page(__entry->pfn),
> -		__entry->pfn,
> -		show_reclaim_flags(__entry->reclaim_flags))
> +	TP_printk("folio=%p lru=%s",
> +		__entry->folio,
> +		__print_symbolic(__entry->lru, LRU_NAMES))
>  );

Why is it useful to print out the folio pointer?  Printing out the PFN
made more sense to me.