sched/numa: Document vma_numab_state fields

[ Upstream commit 9ae5c00ea2e600a8b823f9b95606dd244f3096bf ]

Document the intended usage of the fields.

[ mingo: Reformatted to take less vertical space & tidied it up. ]

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-2-mgorman@techsingularity.net
Stable-dep-of: f22cde4371f3 ("sched/numa: Fix the vma scan starving issue")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index ba25777ec0a7162f093993d5636116563871d583..b53a13d15bbae0f0dc387ec574b6e41dad8a6393 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -551,8 +551,29 @@ struct vma_lock {
 };
 
 struct vma_numab_state {
+       /*
+        * Initialised as time in 'jiffies' after which VMA
+        * should be scanned.  Delays first scan of new VMA by at
+        * least sysctl_numa_balancing_scan_delay:
+        */
        unsigned long next_scan;
+
+       /*
+        * Time in jiffies when access_pids[] is reset to
+        * detect phase change behaviour:
+        */
        unsigned long next_pid_reset;
+
+       /*
+        * Approximate tracking of PIDs that trapped a NUMA hinting
+        * fault. May produce false positives due to hash collisions.
+        *
+        *   [0] Previous PID tracking
+        *   [1] Current PID tracking
+        *
+        * Window moves after next_pid_reset has expired approximately
+        * every VMA_PID_RESET_PERIOD jiffies:
+        */
        unsigned long access_pids[2];
 };