[PATCH v3 3/4] mm/ksm: add tracepoint for ksm advisor

Stefan Roesch
2023-12-04T23:49:26Z

This adds a new tracepoint for the ksm advisor. It reports the last scan
time, the new setting of the pages_to_scan parameter and the average cpu
percent usage of the ksmd background thread for the last scan.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
include/trace/events/ksm.h | 33 +++++++++++++++++++++++++++++++++
mm/ksm.c | 1 +
2 files changed, 34 insertions(+)

diff --git a/include/trace/events/ksm.h b/include/trace/events/ksm.h
index b5ac35c1d0e88..e728647b5d268 100644
--- a/include/trace/events/ksm.h
+++ b/include/trace/events/ksm.h
@@ -245,6 +245,39 @@ TRACE_EVENT(ksm_remove_rmap_item,
__entry->pfn, __entry->rmap_item, __entry->mm)
);

+/**
+ * ksm_advisor - called after the advisor has run
+ *
+ * @scan_time: scan time in seconds
+ * @pages_to_scan: new pages_to_scan value
+ * @cpu_percent: cpu usage in percent
+ *
+ * Allows to trace the ksm advisor.
+ */
+TRACE_EVENT(ksm_advisor,
+
+ TP_PROTO(s64 scan_time, unsigned long pages_to_scan,
+ unsigned int cpu_percent),
+
+ TP_ARGS(scan_time, pages_to_scan, cpu_percent),
+
+ TP_STRUCT__entry(
+ __field(s64, scan_time)
+ __field(unsigned long, pages_to_scan)
+ __field(unsigned int, cpu_percent)
+ ),
+
+ TP_fast_assign(
+ __entry->scan_time = scan_time;
+ __entry->pages_to_scan = pages_to_scan;
+ __entry->cpu_percent = cpu_percent;
+ ),
+
+ TP_printk("ksm scan time %lld pages_to_scan %lu cpu percent %u",
+ __entry->scan_time, __entry->pages_to_scan,
+ __entry->cpu_percent)
+);
+
#endif /* _TRACE_KSM_H */

/* This part must be outside protection */
diff --git a/mm/ksm.c b/mm/ksm.c
index 18b7185bbc65b..b8065c5d5f833 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -455,6 +455,7 @@ static void scan_time_advisor(void)
advisor_ctx.cpu_time = cpu_time;

ksm_thread_pages_to_scan = pages;
+ trace_ksm_advisor(scan_time, pages, cpu_percent);
}

static void run_advisor(void)
--
2.39.3