[PATCH v2 0/2] mm/kmemleak: dedupe verbose scan output

[PATCH v2 0/2] mm/kmemleak: dedupe verbose scan output

[Breno Leitao]

I am starting to run with kmemleak in verbose enabled in some "probe
points" across the my employers fleet so that suspected leaks land in
dmesg without needing a separate read of /sys/kernel/debug/kmemleak.

The downside is that workloads which leak many objects from a single
allocation site flood the console with byte-for-byte identical
backtraces. Hundreds of duplicates per scan are common, drowning out
distinct leaks and unrelated kernel messages, while adding no signal
beyond the first occurrence.

This series collapses those duplicates inside kmemleak itself. Each
unique stackdepot trace_handle prints once per scan, followed by a
short summary line when more than one object shares it:

  kmemleak: unreferenced object 0xff110001083beb00 (size 192):
  kmemleak:   comm "modprobe", pid 974, jiffies 4294754196
  kmemleak:   ...
  kmemleak:   backtrace (crc 6f361828):
  kmemleak:     __kmalloc_cache_noprof+0x1af/0x650
  kmemleak:     ...
  kmemleak:   ... and 71 more object(s) with the same backtrace

The "N new suspected memory leaks" tally and the contents of
/sys/kernel/debug/kmemleak are unchanged - the per-object detail is
still available on demand, only the verbose (dmesg) output is collapsed.

Patch 1 is the kmemleak change.

Patch 2 adds a selftest that loads samples/kmemleak's CONFIG_SAMPLE
kmemleak-test module to generate ten leaks sharing one call site and
checks that the printed count is strictly less than the reported leak
total. Not sure if Patch 2 is useful or not, if not, it is easier to
discard.

Breno Leitao (2):
  mm/kmemleak: dedupe verbose scan output by allocation backtrace
  selftests/mm: add kmemleak verbose dedup test

mm/kmemleak.c                                 | 102 +++++++++++++++++-
 .../selftests/mm/test_kmemleak_dedup.sh       |  78 ++++++++++++++
 2 files changed, 175 insertions(+), 5 deletions(-)
 create mode 100755 tools/testing/selftests/mm/test_kmemleak_dedup.sh
-- 
2.52.0

Signed-off-by: Breno Leitao <leitao@debian.org>

---
Changes in v2:
- Drop struct kmemleak_dedup_entry and its kmalloc. (Catalin)
- Handle trace_handle == 0 instead of dropping it.
- Skip hex dump for coalesced entries (dup_count > 1) — bytes would differ
  across objects sharing a trace anyway, and it removes the only
  object->pointer read left in the deferred path.
- Counter narrowed from unsigned long count to unsigned int dup_count.
- Link to v1: https://patch.msgid.link/20260421-kmemleak_dedup-v1-0-65e31c6cdf0c@debian.org

---
Breno Leitao (2):
      mm/kmemleak: dedupe verbose scan output by allocation backtrace
      selftests/mm: add kmemleak verbose dedup test

 mm/kmemleak.c                                     | 148 ++++++++++++++++++++--
 tools/testing/selftests/mm/Makefile               |   1 +
 tools/testing/selftests/mm/ksft_kmemleak_dedup.sh |  86 +++++++++++++
 3 files changed, 227 insertions(+), 8 deletions(-)
---
base-commit: 4c406406070d57dbefeaad149181785330c23f92
change-id: 20260420-kmemleak_dedup-bee54ffa65e7

Best regards,
--  
Breno Leitao <leitao@debian.org>

[PATCH v2 1/2] mm/kmemleak: dedupe verbose scan output by allocation backtrace

[Breno Leitao]

In kmemleak's verbose mode, every unreferenced object found during a
scan is logged with its full header, hex dump and 16-frame backtrace.
Workloads that leak many objects from a single allocation site flood
dmesg with byte-for-byte identical backtraces, drowning out distinct
leaks and other kernel messages.

Dedupe within each scan using stackdepot's trace_handle as the key: for
every leaked object with a recorded stack trace, look up the
representative kmemleak_object in a per-scan xarray keyed by
trace_handle. The first sighting stores the object pointer (with a
get_object() reference) and sets object->dup_count to 1; later
sightings just bump dup_count on the representative. After the scan,
walk the xarray once and emit each unique backtrace, followed by a
single summary line when more than one object shares it.

Leaks whose trace_handle is 0 (early-boot allocations tracked before
kmemleak_init() set up object_cache, or stack_depot_save() failures
under memory pressure) cannot be deduped, so they are still printed
inline via the same locked OBJECT_ALLOCATED-checked helper. The
contents of /sys/kernel/debug/kmemleak are unchanged - only the
verbose console output is collapsed.

Safety notes:

 - The xarray store happens outside object->lock: object->lock is a
   raw spinlock, while xa_store() may grab xa_node slab locks at a
   higher wait-context level which lockdep flags as invalid.
   trace_handle is captured under object->lock (which serialises with
   kmemleak_update_trace()'s writer), so it is safe to use after
   dropping the lock.

 - get_object() pins the kmemleak_object metadata across
   rcu_read_unlock(), but the underlying tracked allocation can still
   be freed concurrently. The deferred print path therefore re-acquires
   object->lock and re-checks OBJECT_ALLOCATED via print_leak_locked()
   before touching object->pointer; __delete_object() clears that flag
   under the same lock before the user memory goes away. The same
   helper is used by the trace_handle == 0 and xa_store() failure
   fallbacks, so every printer in the new path has identical safety
   guarantees.

 - If get_object() fails after we set OBJECT_REPORTED, the object is
   already being torn down (use_count hit zero); the leak count is
   still accurate but the verbose line is dropped, which is correct
   - the memory was freed concurrently and is no longer a leak.

 - If xa_store() fails to allocate an xa_node under memory pressure,
   we fall back to printing inline via print_leak_locked() instead of
   silently dropping the leak.

 - The hex dump is skipped for coalesced entries (dup_count > 1):
   bytes would differ across objects sharing a backtrace anyway, and
   skipping it removes the only remaining read of object->pointer's
   contents in the deferred path. The representative's reported size
   may also differ from the coalesced objects' sizes; the printed
   trace_handle reflects the representative's current value rather
   than the value used as the dedup key, which is normally - but not
   strictly - identical.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 mm/kmemleak.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 140 insertions(+), 8 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 2eff0d6b622b6..7c7ba17ce7af0 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -92,6 +92,7 @@
 #include <linux/nodemask.h>
 #include <linux/mm.h>
 #include <linux/workqueue.h>
+#include <linux/xarray.h>
 #include <linux/crc32.h>
 
 #include <asm/sections.h>
@@ -157,6 +158,8 @@ struct kmemleak_object {
 	struct hlist_head area_list;
 	unsigned long jiffies;		/* creation timestamp */
 	pid_t pid;			/* pid of the current task */
+	/* per-scan dedup count, valid only while in scan-local dedup xarray */
+	unsigned int dup_count;
 	char comm[TASK_COMM_LEN];	/* executable name */
 };
 
@@ -360,8 +363,9 @@ static const char *__object_type_str(struct kmemleak_object *object)
  * Printing of the unreferenced objects information to the seq file. The
  * print_unreferenced function must be called with the object->lock held.
  */
-static void print_unreferenced(struct seq_file *seq,
-			       struct kmemleak_object *object)
+static void __print_unreferenced(struct seq_file *seq,
+				 struct kmemleak_object *object,
+				 bool hex_dump)
 {
 	int i;
 	unsigned long *entries;
@@ -373,7 +377,8 @@ static void print_unreferenced(struct seq_file *seq,
 			   object->pointer, object->size);
 	warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
 			   object->comm, object->pid, object->jiffies);
-	hex_dump_object(seq, object);
+	if (hex_dump)
+		hex_dump_object(seq, object);
 	warn_or_seq_printf(seq, "  backtrace (crc %x):\n", object->checksum);
 
 	for (i = 0; i < nr_entries; i++) {
@@ -382,6 +387,12 @@ static void print_unreferenced(struct seq_file *seq,
 	}
 }
 
+static void print_unreferenced(struct seq_file *seq,
+			       struct kmemleak_object *object)
+{
+	__print_unreferenced(seq, object, true);
+}
+
 /*
  * Print the kmemleak_object information. This function is used mainly for
  * debugging special cases when kmemleak operations. It must be called with
@@ -1684,6 +1695,103 @@ static void kmemleak_cond_resched(struct kmemleak_object *object)
 	put_object(object);
 }
 
+/*
+ * Print one leak inline. The hex dump is gated on OBJECT_ALLOCATED so it
+ * does not touch user memory that was freed concurrently; the rest of the
+ * report (backtrace, comm, pid) is always emitted since the kmemleak_object
+ * metadata is pinned by the caller.
+ */
+static void print_leak_locked(struct kmemleak_object *object, bool hex_dump)
+{
+	raw_spin_lock_irq(&object->lock);
+	__print_unreferenced(NULL, object,
+			     hex_dump && (object->flags & OBJECT_ALLOCATED));
+	raw_spin_unlock_irq(&object->lock);
+}
+
+/*
+ * Per-scan dedup table for verbose leak printing. The xarray is keyed by
+ * stackdepot trace_handle and stores a pointer to the representative
+ * kmemleak_object. The per-scan repeat count lives in object->dup_count.
+ *
+ * dedup_record() must run outside object->lock: xa_store() may take
+ * mutexes (xa_node slab allocation) which lockdep would flag against the
+ * raw spinlock object->lock.
+ */
+static void dedup_record(struct xarray *dedup, struct kmemleak_object *object,
+			 depot_stack_handle_t trace_handle)
+{
+	struct kmemleak_object *rep;
+	void *old;
+
+	/*
+	 * No stack trace to dedup against: early-boot allocation tracked
+	 * before kmemleak_init() set up object_cache, or stack_depot_save()
+	 * failure under memory pressure.
+	 */
+	if (!trace_handle) {
+		print_leak_locked(object, true);
+		return;
+	}
+
+	/* stack is available, now we can de-dup */
+	rep = xa_load(dedup, trace_handle);
+	if (rep) {
+		rep->dup_count++;
+		return;
+	}
+
+	/*
+	 * Object is being torn down (use_count already hit zero); the
+	 * tracked memory at object->pointer is unsafe to read, so skip.
+	 */
+	if (!get_object(object))
+		return;
+
+	object->dup_count = 1;
+	old = xa_store(dedup, trace_handle, object, GFP_ATOMIC);
+	if (xa_is_err(old)) {
+		/* xa_node allocation failed; fall back to inline print. */
+		print_leak_locked(object, true);
+		put_object(object);
+		return;
+	}
+	/*
+	 * scan_mutex serialises all writers to the dedup xarray, so xa_store()
+	 * after a NULL xa_load() must always overwrite an empty slot.
+	 */
+	WARN_ON_ONCE(old);
+}
+
+/*
+ * Drain the dedup table. Re-acquires object->lock and re-checks
+ * OBJECT_ALLOCATED before printing: while get_object() pins the
+ * kmemleak_object metadata, the underlying tracked allocation may have
+ * been freed since the scan walked it (kmemleak_free clears
+ * OBJECT_ALLOCATED under object->lock before the user memory goes away).
+ * The hex dump is skipped for coalesced entries since the bytes would
+ * differ across objects anyway.
+ */
+static void dedup_flush(struct xarray *dedup)
+{
+	struct kmemleak_object *object;
+	unsigned long idx;
+	unsigned int dup;
+	bool coalesced;
+
+	xa_for_each(dedup, idx, object) {
+		dup = object->dup_count;
+		coalesced = dup > 1;
+
+		print_leak_locked(object, !coalesced);
+		if (coalesced)
+			pr_warn("  ... and %u more object(s) with the same backtrace\n",
+				dup - 1);
+		put_object(object);
+		xa_erase(dedup, idx);
+	}
+}
+
 /*
  * Scan data sections and all the referenced memory blocks allocated via the
  * kernel's standard allocators. This function must be called with the
@@ -1694,6 +1802,7 @@ static void kmemleak_scan(void)
 	struct kmemleak_object *object;
 	struct zone *zone;
 	int __maybe_unused i;
+	struct xarray dedup;
 	int new_leaks = 0;
 
 	jiffies_last_scan = jiffies;
@@ -1834,10 +1943,18 @@ static void kmemleak_scan(void)
 		return;
 
 	/*
-	 * Scanning result reporting.
+	 * Scanning result reporting. When verbose printing is enabled, dedupe
+	 * by stackdepot trace_handle so each unique backtrace is logged once
+	 * per scan, annotated with the number of objects that share it. The
+	 * per-leak count below still reflects every object, and
+	 * /sys/kernel/debug/kmemleak still lists them individually.
 	 */
+	xa_init(&dedup);
 	rcu_read_lock();
 	list_for_each_entry_rcu(object, &object_list, object_list) {
+		depot_stack_handle_t trace_handle;
+		bool dedup_print;
+
 		if (need_resched())
 			kmemleak_cond_resched(object);
 
@@ -1849,18 +1966,33 @@ static void kmemleak_scan(void)
 		if (!color_white(object))
 			continue;
 		raw_spin_lock_irq(&object->lock);
+		trace_handle = 0;
+		dedup_print = false;
 		if (unreferenced_object(object) &&
 		    !(object->flags & OBJECT_REPORTED)) {
 			object->flags |= OBJECT_REPORTED;
-
-			if (kmemleak_verbose)
-				print_unreferenced(NULL, object);
-
+			if (kmemleak_verbose) {
+				trace_handle = object->trace_handle;
+				dedup_print = true;
+			}
 			new_leaks++;
 		}
 		raw_spin_unlock_irq(&object->lock);
+
+		/*
+		 * Defer the verbose print outside object->lock: xa_store()
+		 * may take xa_node slab locks at a higher wait-context level
+		 * which lockdep would flag against the raw_spinlock_t
+		 * object->lock. rcu_read_lock() keeps the kmemleak_object
+		 * alive across the call.
+		 */
+		if (dedup_print)
+			dedup_record(&dedup, object, trace_handle);
 	}
 	rcu_read_unlock();
+	/* Flush'em all */
+	dedup_flush(&dedup);
+	xa_destroy(&dedup);
 
 	if (new_leaks) {
 		kmemleak_found_leaks = true;

-- 
2.52.0

[PATCH v2 2/2] selftests/mm: add kmemleak verbose dedup test

[Breno Leitao]

Exercise the per-scan dedup of kmemleak's verbose leak output added in
the previous commit. The test depends on the kmemleak-test sample
module (CONFIG_SAMPLE_KMEMLEAK=m); load it and unload it to orphan ten
list entries from a single kzalloc() call site that all share one
stackdepot trace_handle, trigger two scans, and assert that the number
of "unreferenced object" lines printed in dmesg is strictly less than
the number of leaks reported. Skip cleanly when kmemleak is absent,
disabled at runtime, or CONFIG_SAMPLE_KMEMLEAK is not built in.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 tools/testing/selftests/mm/Makefile               |  1 +
 tools/testing/selftests/mm/ksft_kmemleak_dedup.sh | 86 +++++++++++++++++++++++
 2 files changed, 87 insertions(+)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index cd24596cdd27e..65ceefb931c3b 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -151,6 +151,7 @@ TEST_PROGS += ksft_gup_test.sh
 TEST_PROGS += ksft_hmm.sh
 TEST_PROGS += ksft_hugetlb.sh
 TEST_PROGS += ksft_hugevm.sh
+TEST_PROGS += ksft_kmemleak_dedup.sh
 TEST_PROGS += ksft_ksm.sh
 TEST_PROGS += ksft_ksm_numa.sh
 TEST_PROGS += ksft_madv_guard.sh
diff --git a/tools/testing/selftests/mm/ksft_kmemleak_dedup.sh b/tools/testing/selftests/mm/ksft_kmemleak_dedup.sh
new file mode 100755
index 0000000000000..1a1b6efd6470a
--- /dev/null
+++ b/tools/testing/selftests/mm/ksft_kmemleak_dedup.sh
@@ -0,0 +1,86 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Verify that kmemleak's verbose scan output deduplicates leaks that share
+# the same allocation backtrace. The kmemleak-test module leaks 10 list
+# entries from a single kzalloc() call site, so they share one stackdepot
+# trace_handle. With dedup, only one "unreferenced object" line should be
+# printed for that backtrace per scan, while the per-scan leak counter
+# still accounts for every object.
+#
+# The expected output is something like:
+#   PASS: kmemleak verbose output deduplicated (11 printed for 61 leaks)
+#
+# Author: Breno Leitao <leitao@debian.org>
+
+ksft_skip=4
+KMEMLEAK=/sys/kernel/debug/kmemleak
+VERBOSE_PARAM=/sys/module/kmemleak/parameters/verbose
+MODULE=kmemleak-test
+
+skip() {
+	echo "SKIP: $*"
+	exit $ksft_skip
+}
+
+fail() {
+	echo "FAIL: $*"
+	exit 1
+}
+
+[ "$(id -u)" -eq 0 ] || skip "must run as root"
+[ -r "$KMEMLEAK" ] || skip "no kmemleak debugfs (CONFIG_DEBUG_KMEMLEAK)"
+[ -w "$VERBOSE_PARAM" ] || skip "kmemleak verbose param missing"
+modinfo "$MODULE" >/dev/null 2>&1 ||
+	skip "$MODULE not built (CONFIG_SAMPLE_KMEMLEAK)"
+
+# kmemleak can be present but disabled at runtime (boot arg kmemleak=off,
+# or it self-disabled after an internal error). In that state writes other
+# than "clear" return EPERM, so probe once and skip if so.
+if ! echo scan > "$KMEMLEAK" 2>/dev/null; then
+	skip "kmemleak is disabled (check dmesg or kmemleak= boot arg)"
+fi
+
+prev_verbose=$(cat "$VERBOSE_PARAM")
+cleanup() {
+	echo "$prev_verbose" > "$VERBOSE_PARAM" 2>/dev/null
+	rmmod "$MODULE" 2>/dev/null
+}
+trap cleanup EXIT
+
+echo 1 > "$VERBOSE_PARAM"
+
+# Drain the existing leak set so the next scan only reports our objects.
+echo clear > "$KMEMLEAK"
+
+modprobe "$MODULE" || fail "failed to load $MODULE"
+# Removing the module orphans the list elements without freeing them.
+rmmod "$MODULE"    || fail "failed to unload $MODULE"
+
+# Two scans: kmemleak requires the object to survive a full scan cycle
+# before it is reported as unreferenced.
+dmesg -C >/dev/null
+echo scan > "$KMEMLEAK"; sleep 6
+echo scan > "$KMEMLEAK"; sleep 6
+
+log=$(dmesg)
+
+new_leaks=$(echo "$log" |
+	sed -n 's/.*kmemleak: \([0-9]\+\) new suspected.*/\1/p' | tail -1)
+[ -n "$new_leaks" ] || fail "no 'new suspected memory leaks' line found"
+
+# Count "unreferenced object" lines emitted in verbose output.
+printed=$(echo "$log" | grep -c 'kmemleak: unreferenced object')
+
+echo "new_leaks=$new_leaks printed=$printed"
+
+# The kzalloc(sizeof(*elem)) loop alone contributes 10 leaks sharing one
+# backtrace, so without dedup printed >= 10. With dedup the printed count
+# must be strictly less than the reported leak total.
+[ "$new_leaks" -ge 10 ] || fail "expected >=10 new leaks, got $new_leaks"
+[ "$printed"   -lt "$new_leaks" ] || \
+	fail "no dedup: printed=$printed new_leaks=$new_leaks"
+
+echo "PASS: kmemleak verbose output deduplicated" \
+	"($printed printed for $new_leaks leaks)"
+exit 0

-- 
2.52.0

Re: [PATCH v2 0/2] mm/kmemleak: dedupe verbose scan output

[Andrew Morton]

On Fri, 24 Apr 2026 08:03:35 -0700 Breno Leitao <leitao@debian.org> wrote:

> I am starting to run with kmemleak in verbose enabled in some "probe
> points" across the my employers fleet so that suspected leaks land in
> dmesg without needing a separate read of /sys/kernel/debug/kmemleak.
> 
> The downside is that workloads which leak many objects from a single
> allocation site flood the console with byte-for-byte identical
> backtraces. Hundreds of duplicates per scan are common, drowning out
> distinct leaks and unrelated kernel messages, while adding no signal
> beyond the first occurrence.
> 
> This series collapses those duplicates inside kmemleak itself. Each
> unique stackdepot trace_handle prints once per scan, followed by a
> short summary line when more than one object shares it:
> 
>   kmemleak: unreferenced object 0xff110001083beb00 (size 192):
>   kmemleak:   comm "modprobe", pid 974, jiffies 4294754196
>   kmemleak:   ...
>   kmemleak:   backtrace (crc 6f361828):
>   kmemleak:     __kmalloc_cache_noprof+0x1af/0x650
>   kmemleak:     ...
>   kmemleak:   ... and 71 more object(s) with the same backtrace
> 
> The "N new suspected memory leaks" tally and the contents of
> /sys/kernel/debug/kmemleak are unchanged - the per-object detail is
> still available on demand, only the verbose (dmesg) output is collapsed.

AI review likes the kernel patch but worries about the selftest:
	https://sashiko.dev/#/patchset/20260424-kmemleak_dedup-v2-0-8bea649b2a92@debian.org

Re: [PATCH v2 1/2] mm/kmemleak: dedupe verbose scan output by allocation backtrace

[Catalin Marinas]

On Fri, Apr 24, 2026 at 08:03:36AM -0700, Breno Leitao wrote:
> In kmemleak's verbose mode, every unreferenced object found during a
> scan is logged with its full header, hex dump and 16-frame backtrace.
> Workloads that leak many objects from a single allocation site flood
> dmesg with byte-for-byte identical backtraces, drowning out distinct
> leaks and other kernel messages.
> 
> Dedupe within each scan using stackdepot's trace_handle as the key: for
> every leaked object with a recorded stack trace, look up the
> representative kmemleak_object in a per-scan xarray keyed by
> trace_handle. The first sighting stores the object pointer (with a
> get_object() reference) and sets object->dup_count to 1; later
> sightings just bump dup_count on the representative. After the scan,
> walk the xarray once and emit each unique backtrace, followed by a
> single summary line when more than one object shares it.
> 
> Leaks whose trace_handle is 0 (early-boot allocations tracked before
> kmemleak_init() set up object_cache, or stack_depot_save() failures
> under memory pressure) cannot be deduped, so they are still printed
> inline via the same locked OBJECT_ALLOCATED-checked helper. The
> contents of /sys/kernel/debug/kmemleak are unchanged - only the
> verbose console output is collapsed.
> 
> Safety notes:
> 
>  - The xarray store happens outside object->lock: object->lock is a
>    raw spinlock, while xa_store() may grab xa_node slab locks at a
>    higher wait-context level which lockdep flags as invalid.
>    trace_handle is captured under object->lock (which serialises with
>    kmemleak_update_trace()'s writer), so it is safe to use after
>    dropping the lock.
> 
>  - get_object() pins the kmemleak_object metadata across
>    rcu_read_unlock(), but the underlying tracked allocation can still
>    be freed concurrently. The deferred print path therefore re-acquires
>    object->lock and re-checks OBJECT_ALLOCATED via print_leak_locked()
>    before touching object->pointer; __delete_object() clears that flag
>    under the same lock before the user memory goes away. The same
>    helper is used by the trace_handle == 0 and xa_store() failure
>    fallbacks, so every printer in the new path has identical safety
>    guarantees.
> 
>  - If get_object() fails after we set OBJECT_REPORTED, the object is
>    already being torn down (use_count hit zero); the leak count is
>    still accurate but the verbose line is dropped, which is correct
>    - the memory was freed concurrently and is no longer a leak.
> 
>  - If xa_store() fails to allocate an xa_node under memory pressure,
>    we fall back to printing inline via print_leak_locked() instead of
>    silently dropping the leak.
> 
>  - The hex dump is skipped for coalesced entries (dup_count > 1):
>    bytes would differ across objects sharing a backtrace anyway, and
>    skipping it removes the only remaining read of object->pointer's
>    contents in the deferred path. The representative's reported size
>    may also differ from the coalesced objects' sizes; the printed
>    trace_handle reflects the representative's current value rather
>    than the value used as the dedup key, which is normally - but not
>    strictly - identical.
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>