[PATCH v2 1/1] system: improve migration debug

[PATCH v2 1/1] system: improve migration debug

[Denis V. Lunev via]

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>
---
Changes from v1:
- adding tracepoint directly to cpu_throttle_set() as suggested by Peter

 system/cpu-throttle.c | 3 +++
 system/trace-events   | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/system/cpu-throttle.c b/system/cpu-throttle.c
index c951a6c65e..7632dc6143 100644
--- 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 2ed1d59b1f..074d001e90 100644
--- 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%%"
-- 
2.40.1

Re: [PATCH v2 1/1] system: improve migration debug

[Peter Xu]

On Thu, Sep 05, 2024 at 09:19:41PM +0200, Denis V. Lunev wrote:
> 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>
> ---
> Changes from v1:
> - adding tracepoint directly to cpu_throttle_set() as suggested by Peter

queued, thanks.

-- 
Peter Xu