[PATCH 0/2] mm: vmscan: add PID and cgroup ID to vmscan tracepoints

[PATCH 0/2] mm: vmscan: add PID and cgroup ID to vmscan tracepoints

[Thomas Ballasi]

Attributing tracepoints to specific processes or cgroups might happen
to be challenging in some scenarios.  Implementing additional context
to these tracepoints with PIDs and cgroup IDs will help improve
analysis.

Signed-off-by: Thomas Ballasi <tballasi@linux.microsoft.com>

Thomas Ballasi (2):
  mm: vmscan: add cgroup IDs to vmscan tracepoints
  mm: vmscan: add PIDs to vmscan tracepoints

 include/trace/events/vmscan.h | 77 +++++++++++++++++++++++------------
 mm/vmscan.c                   | 17 ++++----
 2 files changed, 60 insertions(+), 34 deletions(-)

-- 
2.33.8

[PATCH 1/2] mm: vmscan: add cgroup IDs to vmscan tracepoints

[Thomas Ballasi]

Memory reclaim events are currently difficult to attribute to
specific cgroups, making debugging memory pressure issues
challenging.  This patch adds memory cgroup ID (memcg_id) to key
vmscan tracepoints to enable better correlation and analysis.

For operations not associated with a specific cgroup, the field
is defaulted to 0.

Signed-off-by: Thomas Ballasi <tballasi@linux.microsoft.com>
---
 include/trace/events/vmscan.h | 65 +++++++++++++++++++++--------------
 mm/vmscan.c                   | 17 ++++-----
 2 files changed, 48 insertions(+), 34 deletions(-)

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index d2123dd960d59..afc9f80d03f34 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -114,85 +114,92 @@ TRACE_EVENT(mm_vmscan_wakeup_kswapd,
 
 DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_begin_template,
 
-	TP_PROTO(int order, gfp_t gfp_flags),
+	TP_PROTO(int order, gfp_t gfp_flags, unsigned short memcg_id),
 
-	TP_ARGS(order, gfp_flags),
+	TP_ARGS(order, gfp_flags, memcg_id),
 
 	TP_STRUCT__entry(
 		__field(	int,	order		)
 		__field(	unsigned long,	gfp_flags	)
+		__field(	unsigned short,	memcg_id	)
 	),
 
 	TP_fast_assign(
 		__entry->order		= order;
 		__entry->gfp_flags	= (__force unsigned long)gfp_flags;
+		__entry->memcg_id	= memcg_id;
 	),
 
-	TP_printk("order=%d gfp_flags=%s",
+	TP_printk("order=%d gfp_flags=%s memcg_id=%u",
 		__entry->order,
-		show_gfp_flags(__entry->gfp_flags))
+		show_gfp_flags(__entry->gfp_flags),
+		__entry->memcg_id)
 );
 
 DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_direct_reclaim_begin,
 
-	TP_PROTO(int order, gfp_t gfp_flags),
+	TP_PROTO(int order, gfp_t gfp_flags, unsigned short memcg_id),
 
-	TP_ARGS(order, gfp_flags)
+	TP_ARGS(order, gfp_flags, memcg_id)
 );
 
 #ifdef CONFIG_MEMCG
 DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_memcg_reclaim_begin,
 
-	TP_PROTO(int order, gfp_t gfp_flags),
+	TP_PROTO(int order, gfp_t gfp_flags, unsigned short memcg_id),
 
-	TP_ARGS(order, gfp_flags)
+	TP_ARGS(order, gfp_flags, memcg_id)
 );
 
 DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_memcg_softlimit_reclaim_begin,
 
-	TP_PROTO(int order, gfp_t gfp_flags),
+	TP_PROTO(int order, gfp_t gfp_flags, unsigned short memcg_id),
 
-	TP_ARGS(order, gfp_flags)
+	TP_ARGS(order, gfp_flags, memcg_id)
 );
 #endif /* CONFIG_MEMCG */
 
 DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_end_template,
 
-	TP_PROTO(unsigned long nr_reclaimed),
+	TP_PROTO(unsigned long nr_reclaimed, unsigned short memcg_id),
 
-	TP_ARGS(nr_reclaimed),
+	TP_ARGS(nr_reclaimed, memcg_id),
 
 	TP_STRUCT__entry(
 		__field(	unsigned long,	nr_reclaimed	)
+		__field(	unsigned short,	memcg_id	)
 	),
 
 	TP_fast_assign(
 		__entry->nr_reclaimed	= nr_reclaimed;
+		__entry->memcg_id	= memcg_id;
 	),
 
-	TP_printk("nr_reclaimed=%lu", __entry->nr_reclaimed)
+	TP_printk("nr_reclaimed=%lu memcg_id=%u",
+		__entry->nr_reclaimed,
+		__entry->memcg_id)
 );
 
 DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_direct_reclaim_end,
 
-	TP_PROTO(unsigned long nr_reclaimed),
+	TP_PROTO(unsigned long nr_reclaimed, unsigned short memcg_id),
 
-	TP_ARGS(nr_reclaimed)
+	TP_ARGS(nr_reclaimed, memcg_id)
 );
 
 #ifdef CONFIG_MEMCG
 DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_reclaim_end,
 
-	TP_PROTO(unsigned long nr_reclaimed),
+	TP_PROTO(unsigned long nr_reclaimed, unsigned short memcg_id),
 
-	TP_ARGS(nr_reclaimed)
+	TP_ARGS(nr_reclaimed, memcg_id)
 );
 
 DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_softlimit_reclaim_end,
 
-	TP_PROTO(unsigned long nr_reclaimed),
+	TP_PROTO(unsigned long nr_reclaimed, unsigned short memcg_id),
 
-	TP_ARGS(nr_reclaimed)
+	TP_ARGS(nr_reclaimed, memcg_id)
 );
 #endif /* CONFIG_MEMCG */
 
@@ -209,6 +216,7 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__field(struct shrinker *, shr)
 		__field(void *, shrink)
 		__field(int, nid)
+		__field(unsigned short, memcg_id)
 		__field(long, nr_objects_to_shrink)
 		__field(unsigned long, gfp_flags)
 		__field(unsigned long, cache_items)
@@ -221,6 +229,7 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__entry->shr = shr;
 		__entry->shrink = shr->scan_objects;
 		__entry->nid = sc->nid;
+		__entry->memcg_id = sc->memcg ? mem_cgroup_id(sc->memcg) : 0;
 		__entry->nr_objects_to_shrink = nr_objects_to_shrink;
 		__entry->gfp_flags = (__force unsigned long)sc->gfp_mask;
 		__entry->cache_items = cache_items;
@@ -229,10 +238,11 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__entry->priority = priority;
 	),
 
-	TP_printk("%pS %p: nid: %d objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d",
+	TP_printk("%pS %p: nid: %d memcg_id: %u objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
+		__entry->memcg_id,
 		__entry->nr_objects_to_shrink,
 		show_gfp_flags(__entry->gfp_flags),
 		__entry->cache_items,
@@ -242,15 +252,16 @@ TRACE_EVENT(mm_shrink_slab_start,
 );
 
 TRACE_EVENT(mm_shrink_slab_end,
-	TP_PROTO(struct shrinker *shr, int nid, int shrinker_retval,
+	TP_PROTO(struct shrinker *shr, struct shrink_control *sc, int shrinker_retval,
 		long unused_scan_cnt, long new_scan_cnt, long total_scan),
 
-	TP_ARGS(shr, nid, shrinker_retval, unused_scan_cnt, new_scan_cnt,
+	TP_ARGS(shr, sc, shrinker_retval, unused_scan_cnt, new_scan_cnt,
 		total_scan),
 
 	TP_STRUCT__entry(
 		__field(struct shrinker *, shr)
 		__field(int, nid)
+		__field(unsigned short, memcg_id)
 		__field(void *, shrink)
 		__field(long, unused_scan)
 		__field(long, new_scan)
@@ -260,7 +271,8 @@ TRACE_EVENT(mm_shrink_slab_end,
 
 	TP_fast_assign(
 		__entry->shr = shr;
-		__entry->nid = nid;
+		__entry->nid = sc->nid;
+		__entry->memcg_id = sc->memcg ? mem_cgroup_id(sc->memcg) : 0;
 		__entry->shrink = shr->scan_objects;
 		__entry->unused_scan = unused_scan_cnt;
 		__entry->new_scan = new_scan_cnt;
@@ -268,10 +280,11 @@ TRACE_EVENT(mm_shrink_slab_end,
 		__entry->total_scan = total_scan;
 	),
 
-	TP_printk("%pS %p: nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
+	TP_printk("%pS %p: nid: %d memcg_id: %u unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
+		__entry->memcg_id,
 		__entry->unused_scan,
 		__entry->new_scan,
 		__entry->total_scan,
@@ -463,9 +476,9 @@ TRACE_EVENT(mm_vmscan_node_reclaim_begin,
 
 DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_node_reclaim_end,
 
-	TP_PROTO(unsigned long nr_reclaimed),
+	TP_PROTO(unsigned long nr_reclaimed, unsigned short memcg_id),
 
-	TP_ARGS(nr_reclaimed)
+	TP_ARGS(nr_reclaimed, memcg_id)
 );
 
 TRACE_EVENT(mm_vmscan_throttled,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 258f5472f1e90..0e65ec3a087a5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -931,7 +931,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 	 */
 	new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
 
-	trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
+	trace_mm_shrink_slab_end(shrinker, shrinkctl, freed, nr, new_nr, total_scan);
 	return freed;
 }
 
@@ -7092,11 +7092,11 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 		return 1;
 
 	set_task_reclaim_state(current, &sc.reclaim_state);
-	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
+	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask, 0);
 
 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
 
-	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
+	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed, 0);
 	set_task_reclaim_state(current, NULL);
 
 	return nr_reclaimed;
@@ -7126,7 +7126,8 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
 			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
 
 	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
-						      sc.gfp_mask);
+						      sc.gfp_mask,
+						      mem_cgroup_id(memcg));
 
 	/*
 	 * NOTE: Although we can get the priority field, using it
@@ -7137,7 +7138,7 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
 	 */
 	shrink_lruvec(lruvec, &sc);
 
-	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
+	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed, mem_cgroup_id(memcg));
 
 	*nr_scanned = sc.nr_scanned;
 
@@ -7171,13 +7172,13 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
 
 	set_task_reclaim_state(current, &sc.reclaim_state);
-	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
+	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask, mem_cgroup_id(memcg));
 	noreclaim_flag = memalloc_noreclaim_save();
 
 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
 
 	memalloc_noreclaim_restore(noreclaim_flag);
-	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed, mem_cgroup_id(memcg));
 	set_task_reclaim_state(current, NULL);
 
 	return nr_reclaimed;
@@ -8072,7 +8073,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 	fs_reclaim_release(sc.gfp_mask);
 	psi_memstall_leave(&pflags);
 
-	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
+	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed, 0);
 
 	return sc.nr_reclaimed >= nr_pages;
 }
-- 
2.33.8

[PATCH 2/2] mm: vmscan: add PIDs to vmscan tracepoints

[Thomas Ballasi]

The changes aims at adding additionnal tracepoints variables to help
debuggers attribute them to specific processes.

The PID field uses in_task() to reliably detect when we're in process
context and can safely access current->pid.  When not in process
context (such as in interrupt or in an asynchronous RCU context), the
field is set to -1 as a sentinel value.

Signed-off-by: Thomas Ballasi <tballasi@linux.microsoft.com>
---
 include/trace/events/vmscan.h | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index afc9f80d03f34..eddb4e75e2e23 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -121,18 +121,21 @@ DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_begin_template,
 	TP_STRUCT__entry(
 		__field(	int,	order		)
 		__field(	unsigned long,	gfp_flags	)
+		__field(	int,	pid		)
 		__field(	unsigned short,	memcg_id	)
 	),
 
 	TP_fast_assign(
 		__entry->order		= order;
 		__entry->gfp_flags	= (__force unsigned long)gfp_flags;
+		__entry->pid		= in_task() ? current->pid : -1;
 		__entry->memcg_id	= memcg_id;
 	),
 
-	TP_printk("order=%d gfp_flags=%s memcg_id=%u",
+	TP_printk("order=%d gfp_flags=%s pid=%d memcg_id=%u",
 		__entry->order,
 		show_gfp_flags(__entry->gfp_flags),
+		__entry->pid,
 		__entry->memcg_id)
 );
 
@@ -167,16 +170,19 @@ DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_end_template,
 
 	TP_STRUCT__entry(
 		__field(	unsigned long,	nr_reclaimed	)
+		__field(	int,	pid		)
 		__field(	unsigned short,	memcg_id	)
 	),
 
 	TP_fast_assign(
 		__entry->nr_reclaimed	= nr_reclaimed;
+		__entry->pid		= in_task() ? current->pid : -1;
 		__entry->memcg_id	= memcg_id;
 	),
 
-	TP_printk("nr_reclaimed=%lu memcg_id=%u",
+	TP_printk("nr_reclaimed=%lu pid=%d memcg_id=%u",
 		__entry->nr_reclaimed,
+		__entry->pid,
 		__entry->memcg_id)
 );
 
@@ -216,6 +222,7 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__field(struct shrinker *, shr)
 		__field(void *, shrink)
 		__field(int, nid)
+		__field(int, pid)
 		__field(unsigned short, memcg_id)
 		__field(long, nr_objects_to_shrink)
 		__field(unsigned long, gfp_flags)
@@ -229,6 +236,7 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__entry->shr = shr;
 		__entry->shrink = shr->scan_objects;
 		__entry->nid = sc->nid;
+		__entry->pid = in_task() ? current->pid : -1;
 		__entry->memcg_id = sc->memcg ? mem_cgroup_id(sc->memcg) : 0;
 		__entry->nr_objects_to_shrink = nr_objects_to_shrink;
 		__entry->gfp_flags = (__force unsigned long)sc->gfp_mask;
@@ -238,10 +246,11 @@ TRACE_EVENT(mm_shrink_slab_start,
 		__entry->priority = priority;
 	),
 
-	TP_printk("%pS %p: nid: %d memcg_id: %u objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d",
+	TP_printk("%pS %p: nid: %d pid: %d memcg_id: %u objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
+		__entry->pid,
 		__entry->memcg_id,
 		__entry->nr_objects_to_shrink,
 		show_gfp_flags(__entry->gfp_flags),
@@ -261,6 +270,7 @@ TRACE_EVENT(mm_shrink_slab_end,
 	TP_STRUCT__entry(
 		__field(struct shrinker *, shr)
 		__field(int, nid)
+		__field(int, pid)
 		__field(unsigned short, memcg_id)
 		__field(void *, shrink)
 		__field(long, unused_scan)
@@ -272,6 +282,7 @@ TRACE_EVENT(mm_shrink_slab_end,
 	TP_fast_assign(
 		__entry->shr = shr;
 		__entry->nid = sc->nid;
+		__entry->pid = in_task() ? current->pid : -1;
 		__entry->memcg_id = sc->memcg ? mem_cgroup_id(sc->memcg) : 0;
 		__entry->shrink = shr->scan_objects;
 		__entry->unused_scan = unused_scan_cnt;
@@ -280,10 +291,11 @@ TRACE_EVENT(mm_shrink_slab_end,
 		__entry->total_scan = total_scan;
 	),
 
-	TP_printk("%pS %p: nid: %d memcg_id: %u unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
+	TP_printk("%pS %p: nid: %d pid: %d memcg_id: %u unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
+		__entry->pid,
 		__entry->memcg_id,
 		__entry->unused_scan,
 		__entry->new_scan,
-- 
2.33.8

Re: [PATCH 2/2] mm: vmscan: add PIDs to vmscan tracepoints

[Steven Rostedt]

On Mon,  8 Dec 2025 10:14:13 -0800
Thomas Ballasi <tballasi@linux.microsoft.com> wrote:

> ---
>  include/trace/events/vmscan.h | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index afc9f80d03f34..eddb4e75e2e23 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -121,18 +121,21 @@ DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_begin_template,
>  	TP_STRUCT__entry(
>  		__field(	int,	order		)
>  		__field(	unsigned long,	gfp_flags	)
> +		__field(	int,	pid		)

This puts a hole in the ring buffer on 64 bit machines. Please keep pid
next to order as they are both 'int' and not have an "unsigned long"
between the two.

>  		__field(	unsigned short,	memcg_id	)
>  	),

-- Steve