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

[Thomas Ballasi <tballasi@linux.microsoft.com>]

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