+ mm-vmscan-add-balance_pgdat-begin-end-tracepoints.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmscan: add balance_pgdat begin/end tracepoints
has been added to the -mm mm-new branch.  Its filename is
     mm-vmscan-add-balance_pgdat-begin-end-tracepoints.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-add-balance_pgdat-begin-end-tracepoints.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Bunyod Suvonov <b.suvonov@sjtu.edu.cn>
Subject: mm/vmscan: add balance_pgdat begin/end tracepoints
Date: Thu, 23 Apr 2026 18:37:53 +0800

Vmscan has six main reclaim entry points: try_to_free_pages() for direct
reclaim, try_to_free_mem_cgroup_pages() for memcg reclaim,
mem_cgroup_shrink_node() for memcg soft limit reclaim, node_reclaim() for
node reclaim, shrink_all_memory() for hibernation reclaim, and
balance_pgdat() for kswapd reclaim.

All of them, except for shrink_all_memory() and balance_pgdat(), already
have begin/end tracepoints.  This makes it harder to trace which reclaim
path is responsible for memory reclaim activity, because kswapd reclaim
cannot be identified as cleanly as other reclaim entry points, even though
it is the main background reclaim path under memory pressure.  There may
be no need to trace shrink_all_memory() as it is primarily used during
hibernation.  So this patch adds the missing tracepoint pair for
balance_pgdat().

The begin tracepoint records the node id, requested reclaim order, and
highest_zoneidx.  The end tracepoint records the node id, reclaim order
that balance_pgdat() finished with, highest_zoneidx, and nr_reclaimed. 
Together, they show the requested reclaim order and zone bound, whether
reclaim fell back to a lower order, and how much reclaim work was done.

Link: https://lore.kernel.org/20260423103753.546582-1-b.suvonov@sjtu.edu.cn
Signed-off-by: Bunyod Suvonov <b.suvonov@sjtu.edu.cn>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/trace/events/vmscan.h |   52 ++++++++++++++++++++++++++++++++
 mm/vmscan.c                   |    5 +++
 2 files changed, 57 insertions(+)

--- a/include/trace/events/vmscan.h~mm-vmscan-add-balance_pgdat-begin-end-tracepoints
+++ a/include/trace/events/vmscan.h
@@ -96,6 +96,58 @@ TRACE_EVENT(mm_vmscan_kswapd_wake,
 		__entry->order)
 );
 
+TRACE_EVENT(mm_vmscan_balance_pgdat_begin,
+
+	TP_PROTO(int nid, int order, int highest_zoneidx),
+
+	TP_ARGS(nid, order, highest_zoneidx),
+
+	TP_STRUCT__entry(
+		__field(int, nid)
+		__field(int, order)
+		__field(int, highest_zoneidx)
+	),
+
+	TP_fast_assign(
+		__entry->nid = nid;
+		__entry->order = order;
+		__entry->highest_zoneidx = highest_zoneidx;
+	),
+
+	TP_printk("nid=%d order=%d highest_zoneidx=%-8s",
+		__entry->nid,
+		__entry->order,
+		__print_symbolic(__entry->highest_zoneidx, ZONE_TYPE))
+);
+
+TRACE_EVENT(mm_vmscan_balance_pgdat_end,
+
+	TP_PROTO(int nid, int order, int highest_zoneidx,
+		 unsigned long nr_reclaimed),
+
+	TP_ARGS(nid, order, highest_zoneidx, nr_reclaimed),
+
+	TP_STRUCT__entry(
+		__field(int, nid)
+		__field(int, order)
+		__field(int, highest_zoneidx)
+		__field(unsigned long, nr_reclaimed)
+	),
+
+	TP_fast_assign(
+		__entry->nid = nid;
+		__entry->order = order;
+		__entry->highest_zoneidx = highest_zoneidx;
+		__entry->nr_reclaimed = nr_reclaimed;
+	),
+
+	TP_printk("nid=%d order=%d highest_zoneidx=%-8s nr_reclaimed=%lu",
+		__entry->nid,
+		__entry->order,
+		__print_symbolic(__entry->highest_zoneidx, ZONE_TYPE),
+		__entry->nr_reclaimed)
+);
+
 TRACE_EVENT(mm_vmscan_wakeup_kswapd,
 
 	TP_PROTO(int nid, int zid, int order, gfp_t gfp_flags),
--- a/mm/vmscan.c~mm-vmscan-add-balance_pgdat-begin-end-tracepoints
+++ a/mm/vmscan.c
@@ -7121,6 +7121,8 @@ static int balance_pgdat(pg_data_t *pgda
 		.may_unmap = 1,
 	};
 
+	trace_mm_vmscan_balance_pgdat_begin(pgdat->node_id, order,
+					    highest_zoneidx);
 	set_task_reclaim_state(current, &sc.reclaim_state);
 	psi_memstall_enter(&pflags);
 	__fs_reclaim_acquire(_THIS_IP_);
@@ -7314,6 +7316,9 @@ out:
 	psi_memstall_leave(&pflags);
 	set_task_reclaim_state(current, NULL);
 
+	trace_mm_vmscan_balance_pgdat_end(pgdat->node_id, sc.order,
+					  highest_zoneidx, sc.nr_reclaimed);
+
 	/*
 	 * Return the order kswapd stopped reclaiming at as
 	 * prepare_kswapd_sleep() takes it into account. If another caller
_

Patches currently in -mm which might be from b.suvonov@sjtu.edu.cn are

mm-vmscan-add-balance_pgdat-begin-end-tracepoints.patch