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

Breno Leitao
2026-04-21T14:13:38Z

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>

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

mm/kmemleak.c | 113 +++++++++++++++++++++-
tools/testing/selftests/mm/test_kmemleak_dedup.sh | 86 ++++++++++++++++
2 files changed, 197 insertions(+), 2 deletions(-)
---
base-commit: 97e797263a5e963da3d1e66e743fd518567dfe37
change-id: 20260420-kmemleak_dedup-bee54ffa65e7

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