system: improve migration debug

Right now migration_throttle() tracepoint lacks very important
important information, i.e. no one could easily say how much the guest
is throttled. This makes difficult to debug guest quality of service
during migration.

This patch adds one more tracepoint into cpu_throttle_set() which is
actually doing this job.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Peter Xu <peterx@redhat.com>
CC: Fabiano Rosas <farosas@suse.de>
CC: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20240905191941.310592-1-den@openvz.org
Signed-off-by: Peter Xu <peterx@redhat.com>

diff --git a/system/cpu-throttle.c b/system/cpu-throttle.c
index c951a6c65e1996bd26eb57c605a2e0f3a1b1c020..7632dc6143834c3679ed671adb9f76751c20cd45 100644 (file)
--- a/system/cpu-throttle.c
+++ b/system/cpu-throttle.c
@@ -28,6 +28,7 @@
 #include "qemu/main-loop.h"
 #include "sysemu/cpus.h"
 #include "sysemu/cpu-throttle.h"
+#include "trace.h"
 
 /* vcpu throttling controls */
 static QEMUTimer *throttle_timer;
@@ -95,6 +96,8 @@ void cpu_throttle_set(int new_throttle_pct)
      */
     bool throttle_active = cpu_throttle_active();
 
+    trace_cpu_throttle_set(new_throttle_pct);
+
     /* Ensure throttle percentage is within valid range */
     new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
     new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);

diff --git a/system/trace-events b/system/trace-events
index 2ed1d59b1fb0de8d7fd73b96156abb9fc2063c4d..074d001e906e33f58818f50bc41a894d29e80846 100644 (file)
--- a/system/trace-events
+++ b/system/trace-events
@@ -44,3 +44,6 @@ dirtylimit_state_finalize(void)
 dirtylimit_throttle_pct(int cpu_index, uint64_t pct, int64_t time_us) "CPU[%d] throttle percent: %" PRIu64 ", throttle adjust time %"PRIi64 " us"
 dirtylimit_set_vcpu(int cpu_index, uint64_t quota) "CPU[%d] set dirty page rate limit %"PRIu64
 dirtylimit_vcpu_execute(int cpu_index, int64_t sleep_time_us) "CPU[%d] sleep %"PRIi64 " us"
+
+# cpu-throttle.c
+cpu_throttle_set(int new_throttle_pct)  "set guest CPU throttled by %d%%"