On 2/19/21 9:08 PM, Aleksei Zakharov wrote:
This patch adds delay time (steal time inside guest) to libvirt
domain per-vcpu stats. Delay time is an important performance metric.
It is a consequence of the overloaded CPU. Knowledge of the delay
time of a virtual machine helps to understand if it is affected and
estimate the impact.
As a result, it is possible to react exactly when needed and
rebalance the load between hosts. This is used by cloud providers
to provide quality of service, especially when the CPU is
oversubscribed.
It's more convenient to work with this metric in a context of a
libvirt domain. Any monitoring software may use this information.
Signed-off-by: Aleksei Zakharov <zaharov@xxxxxxxxxxx>
---
docs/manpages/virsh.rst | 4 ++++
src/libvirt-domain.c | 4 ++++
src/qemu/qemu_driver.c | 44 +++++++++++++++++++++++++++++++++++++++--
3 files changed, 50 insertions(+), 2 deletions(-)
diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
index e3afa48f7b..a2b83ddfaa 100644
--- a/docs/manpages/virsh.rst
+++ b/docs/manpages/virsh.rst
@@ -2295,6 +2295,10 @@ When selecting the *--state* group the following fields are returned:
* ``vcpu.<num>.halted`` - virtual CPU <num> is halted: yes or
no (may indicate the processor is idle or even disabled,
depending on the architecture)
+* ``vcpu.<num>.delay`` - time the vCPU <num> thread was enqueued by the
+ host scheduler, but was waiting in the queue instead of running.
+ Exposed to the VM as a steal time.
+
*--interface* returns:
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
index 4af0166872..e54d11e513 100644
--- a/src/libvirt-domain.c
+++ b/src/libvirt-domain.c
@@ -11693,6 +11693,10 @@ virConnectGetDomainCapabilities(virConnectPtr conn,
* "vcpu.<num>.halted" - virtual CPU <num> is halted, may indicate the
* processor is idle or even disabled, depending
* on the architecture)
+ * "vcpu.<num>.delay" - time the vCPU <num> thread was enqueued by the
+ * host scheduler, but was waiting in the queue
+ * instead of running. Exposed to the VM as a steal
+ * time.
*
* VIR_DOMAIN_STATS_INTERFACE:
* Return network interface statistics (from domain point of view).
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index b9bbdf8d48..9ec3c8fce7 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1332,6 +1332,34 @@ static char *qemuConnectGetCapabilities(virConnectPtr conn) {
return virCapabilitiesFormatXML(caps);
}
+static int
+qemuGetSchedstatDelay(unsigned long long *cpudelay,
+ pid_t pid, pid_t tid)
+{
I know you took inspiration in existing code, but our standards have
moved since that code was written, a bit.
+ g_autofree char *proc = NULL;
+ unsigned long long oncpu = 0;
+ g_autofree FILE *schedstat = NULL;
+
+ if (tid)
+ proc = g_strdup_printf("/proc/%d/task/%d/schedstat", (int)pid, (int)tid);
+ else
+ proc = g_strdup_printf("/proc/%d/schedstat", (int)pid);
+
+ schedstat = fopen(proc, "r");
+ if (!schedstat) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Unable to open schedstat file at '%s'"),
+ proc);
I'd expect this to be an error. Except for the case when the file
doesn't exist.
+ }
+ if (fscanf(schedstat, "%llu %llu", &oncpu, cpudelay) < 2) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Unable to parse schedstat info at '%s'"),
+ proc);
And this has to be error always.
+ }
+
+ VIR_FORCE_FCLOSE(schedstat);
+ return 0;
I'm fixing this function a bit.
+}
The rest looks okay. I'm pushing it.
Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
Congratulations on your first libvirt contribution!
Michal
