Re: [PATCH v3 2/2] mm/vmscan: add tracepoint and reason for kswapd_failures reset

On Wed, Jan 14, 2026 at 03:40:36PM +0800, Jiayuan Chen wrote:

From: Jiayuan Chen <redacted>

Currently, kswapd_failures is reset in multiple places (kswapd,
direct reclaim, PCP freeing, memory-tiers), but there's no way to
trace when and why it was reset, making it difficult to debug
memory reclaim issues.

This patch:

1. Introduce pgdat_reset_kswapd_failures() as a wrapper function to
   centralize kswapd_failures reset logic.

2. Add reset_kswapd_failures_reason enum to distinguish reset sources:
   - RESET_KSWAPD_FAILURES_KSWAPD: reset from kswapd context
   - RESET_KSWAPD_FAILURES_DIRECT: reset from direct reclaim
   - RESET_KSWAPD_FAILURES_PCP: reset from PCP page freeing
   - RESET_KSWAPD_FAILURES_OTHER: reset from other paths

3. Add tracepoints for better observability:
   - mm_vmscan_reset_kswapd_failures: traces each reset with reason
   - mm_vmscan_kswapd_reclaim_fail: traces each kswapd reclaim failure

---
Test results:

$ trace-cmd record -e vmscan:mm_vmscan_reset_kswapd_failures -e vmscan:mm_vmscan_kswapd_reclaim_fail
$ # generate memory pressure
$ trace-cmd report
cpus=4
kswapd1-73  [002]  24.863112: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=1
kswapd1-73  [002]  24.863472: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=2
kswapd1-73  [002]  24.863813: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=3
kswapd1-73  [002]  24.864141: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=4
kswapd1-73  [002]  24.864462: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=5
kswapd1-73  [002]  24.864779: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=6
kswapd1-73  [002]  24.865103: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=7
kswapd1-73  [002]  24.865421: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=8
kswapd1-73  [002]  24.865737: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=9
kswapd1-73  [002]  24.866070: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=10
kswapd1-73  [002]  24.866385: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=11
kswapd1-73  [002]  24.866701: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=12
kswapd1-73  [002]  24.867016: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=13
kswapd1-73  [002]  24.867333: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=14
kswapd1-73  [002]  24.867649: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=15
kswapd1-73  [002]  24.867965: mm_vmscan_kswapd_reclaim_fail: nid=1 failures=16
kswapd0-72  [001]  25.020464: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=1
kswapd0-72  [001]  25.021054: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=2
kswapd0-72  [001]  25.021628: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=3
kswapd0-72  [001]  25.022217: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=4
kswapd0-72  [001]  25.022790: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=5
kswapd0-72  [001]  25.023366: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=6
kswapd0-72  [001]  25.023937: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=7
kswapd0-72  [001]  25.024511: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=8
kswapd0-72  [001]  25.025092: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=9
kswapd0-72  [001]  25.025665: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=10
kswapd0-72  [001]  25.026249: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=11
kswapd0-72  [001]  25.026824: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=12
kswapd0-72  [001]  25.027398: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=13
kswapd0-72  [001]  25.027976: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=14
kswapd0-72  [001]  25.028554: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=15
kswapd0-72  [001]  25.029140: mm_vmscan_kswapd_reclaim_fail: nid=0 failures=16
ann-416     [002]  25.577925: mm_vmscan_reset_kswapd_failures: nid=0 reason=PCP
dd-417      [002]  35.111721: mm_vmscan_reset_kswapd_failures: nid=1 reason=DIRECT

Signed-off-by: Jiayuan Chen <redacted>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>

Thanks for adding this.

Acked-by: Shakeel Butt <shakeel.butt@linux.dev>