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qemu: add reporting of vCPU wait time

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The VIR_DOMAIN_STATS_VCPU flag to virDomainListGetStats
enables reporting of stats about vCPUs. Currently we
only report the cumulative CPU running time and the
execution state.

This adds reporting of the wait time - time the vCPU
wants to run, but the host scheduler has something else
running ahead of it.

The data is reported per-vCPU eg

$ virsh domstats --vcpu demo
 Domain: 'demo'
   vcpu.current=4
   vcpu.maximum=4
   vcpu.0.state=1
   vcpu.0.time=1420000000
   vcpu.0.wait=18403928
   vcpu.1.state=1
   vcpu.1.time=130000000
   vcpu.1.wait=10612111
   vcpu.2.state=1
   vcpu.2.time=110000000
   vcpu.2.wait=12759501
   vcpu.3.state=1
   vcpu.3.time=90000000
   vcpu.3.wait=21825087

In implementing this I notice our reporting of CPU execute
time has very poor granularity, since we are getting it
from /proc/$PID/stat. As a future enhancement we should
prefer to get CPU execute time from /proc/$PID/schedstat
or /proc/$PID/sched (if either exist on the running kernel)

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2015-12-10 14:37:01 +00:00
parent 985f01a65f
commit 511e7c5bba
1 changed files with 98 additions and 4 deletions
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102
src/qemu/qemu_driver.c
View File

@ -1360,6 +1360,82 @@ static char *qemuConnectGetCapabilities(virConnectPtr conn) {
}
static int
qemuGetSchedInfo(unsigned long long *cpuWait,
pid_t pid, pid_t tid)
{
char *proc = NULL;
char *data = NULL;
char **lines = NULL;
size_t i;
int ret = -1;
double val;
*cpuWait = 0;
/* In general, we cannot assume pid_t fits in int; but /proc parsing
* is specific to Linux where int works fine. */
if (tid)
ret = virAsprintf(&proc, "/proc/%d/task/%d/sched", (int)pid, (int)tid);
else
ret = virAsprintf(&proc, "/proc/%d/sched", (int)pid);
if (ret < 0)
goto cleanup;
ret = -1;
/* The file is not guaranteed to exist (needs CONFIG_SCHED_DEBUG) */
if (access(proc, R_OK) < 0) {
ret = 0;
goto cleanup;
}
if (virFileReadAll(proc, (1<<16), &data) < 0)
goto cleanup;
lines = virStringSplit(data, "\n", 0);
if (!lines)
goto cleanup;
for (i = 0; lines[i] != NULL; i++) {
const char *line = lines[i];
/* Needs CONFIG_SCHEDSTATS. The second check
* is the old name the kernel used in past */
if (STRPREFIX(line, "se.statistics.wait_sum") ||
STRPREFIX(line, "se.wait_sum")) {
line = strchr(line, ':');
if (!line) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("Missing separator in sched info '%s'"),
lines[i]);
goto cleanup;
}
line++;
while (*line == ' ')
line++;
if (virStrToDouble(line, NULL, &val) < 0) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("Unable to parse sched info value '%s'"),
line);
goto cleanup;
}
*cpuWait = (unsigned long long)(val * 1000000);
break;
}
}
ret = 0;
cleanup:
VIR_FREE(data);
VIR_FREE(proc);
VIR_FREE(lines);
return ret;
}
static int
qemuGetProcessInfo(unsigned long long *cpuTime, int *lastCpu, long *vm_rss,
pid_t pid, int tid)
@ -1424,6 +1500,7 @@ qemuGetProcessInfo(unsigned long long *cpuTime, int *lastCpu, long *vm_rss,
static int
qemuDomainHelperGetVcpus(virDomainObjPtr vm,
virVcpuInfoPtr info,
unsigned long long *cpuwait,
int maxinfo,
unsigned char *cpumaps,
int maplen)
@ -1476,6 +1553,11 @@ qemuDomainHelperGetVcpus(virDomainObjPtr vm,
virBitmapFree(map);
}
if (cpuwait) {
if (qemuGetSchedInfo(&(cpuwait[i]), vm->pid, vcpupid) < 0)
return -1;
}
ncpuinfo++;
}
@ -5490,7 +5572,7 @@ qemuDomainGetVcpus(virDomainPtr dom,
goto cleanup;
}
ret = qemuDomainHelperGetVcpus(vm, info, maxinfo, cpumaps, maplen);
ret = qemuDomainHelperGetVcpus(vm, info, NULL, maxinfo, cpumaps, maplen);
cleanup:
virDomainObjEndAPI(&vm);
@ -19034,6 +19116,7 @@ qemuDomainGetStatsVcpu(virQEMUDriverPtr driver ATTRIBUTE_UNUSED,
int ret = -1;
char param_name[VIR_TYPED_PARAM_FIELD_LENGTH];
virVcpuInfoPtr cpuinfo = NULL;
unsigned long long *cpuwait = NULL;
if (virTypedParamsAddUInt(&record->params,
&record->nparams,
@ -19049,10 +19132,12 @@ qemuDomainGetStatsVcpu(virQEMUDriverPtr driver ATTRIBUTE_UNUSED,
virDomainDefGetVcpusMax(dom->def)) < 0)
return -1;
if (VIR_ALLOC_N(cpuinfo, virDomainDefGetVcpus(dom->def)) < 0)
return -1;
if (VIR_ALLOC_N(cpuinfo, virDomainDefGetVcpus(dom->def)) < 0 ||
VIR_ALLOC_N(cpuwait, virDomainDefGetVcpus(dom->def)) < 0)
goto cleanup;
if (qemuDomainHelperGetVcpus(dom, cpuinfo, virDomainDefGetVcpus(dom->def),
if (qemuDomainHelperGetVcpus(dom, cpuinfo, cpuwait,
virDomainDefGetVcpus(dom->def),
NULL, 0) < 0) {
virResetLastError();
ret = 0; /* it's ok to be silent and go ahead */
@ -19081,12 +19166,21 @@ qemuDomainGetStatsVcpu(virQEMUDriverPtr driver ATTRIBUTE_UNUSED,
param_name,
cpuinfo[i].cpuTime) < 0)
goto cleanup;
snprintf(param_name, VIR_TYPED_PARAM_FIELD_LENGTH,
"vcpu.%zu.wait", i);
if (virTypedParamsAddULLong(&record->params,
&record->nparams,
maxparams,
param_name,
cpuwait[i]) < 0)
goto cleanup;
}
ret = 0;
cleanup:
VIR_FREE(cpuinfo);
VIR_FREE(cpuwait);
return ret;
}