This patch add the ability to statistic the halt polling time when
VM execute HLT(arm is WFI).
In actual services, the execution of the HLT instruction by the
guest is an important cause of virtualization overhead. The halt
polling feature is introduced to solve this problem. When a guest
idle VM exit occurs, the host continues polling for a period of
time to reduce the guest service delay. This mechanism may cause
the CPU usage to be 100% when the physical CPU is idle. If the
guest service model is woken up at an interval to process a small
amount of traffic, and the interval is shorter than kvm halt_poll_ns.
The host polls the block time of the entire VM and the CPU usage
increases to 100%.
The kernel provides the capability of collecting statistics on the
halt polling time after v5.8, Introduced by commit
<cb953129bfe5c0f2da835a0469930873fb7e71df>. It is rendered in debugfs.
Therefore, we can use this kernel feature to provide the halt poll
time to the user to obtain a more accurate CPU usage as required.
Signed-off-by: Yang Fei <yangfei85@xxxxxxxxxx>
---
src/libvirt_private.syms | 2 +
src/qemu/qemu_driver.c | 29 +++++++++++++
src/util/virutil.c | 89 ++++++++++++++++++++++++++++++++++++++++
src/util/virutil.h | 9 ++++
4 files changed, 129 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 68e4b6aab8..f92213b8c2 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3479,6 +3479,8 @@ virDoesUserExist;
virDoubleToStr;
virFormatIntDecimal;
virFormatIntPretty;
+virGetCpuHaltPollTime;
+virGetDebugFsKvmValue;
virGetDeviceID;
virGetDeviceUnprivSGIO;
virGetGroupID;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 235f575901..3a2b530ecf 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -17812,6 +17812,32 @@ qemuDomainGetStatsCpuCache(virQEMUDriver *driver,
return ret;
}
+#ifdef __linux__
+static int
+qemuDomainGetStatsCpuHaltPollTime(virDomainObj *dom,
+ virTypedParamList *params)
+{
+ unsigned long long haltPollSuccess = 0;
+ unsigned long long haltPollFail = 0;
+ pid_t pid = dom->pid;
+
+ if (virGetCpuHaltPollTime(pid, &haltPollSuccess, &haltPollFail) != 0)
+ return -1;
+ if (virTypedParamListAddULLong(params, haltPollSuccess, "haltpollsuccess.time") < 0)
+ return -1;
+ if (virTypedParamListAddULLong(params, haltPollFail, "haltpollfail.time") < 0)
+ return -1;
+
+ return 0;
+}
+#else
+static int
+qemuDomainGetStatsCpuHaltPollTime(virDomainObj *dom,
+ virTypedParamList *params)
+{
+ return -1;
+}
+#endif
static int
qemuDomainGetStatsCpuCgroup(virDomainObj *dom,
@@ -17852,6 +17878,9 @@ qemuDomainGetStatsCpu(virQEMUDriver *driver,
if (qemuDomainGetStatsCpuCache(driver, dom, params) < 0)
return -1;
+ if (qemuDomainGetStatsCpuHaltPollTime(dom, params) < 0)
+ return -1;
+
return 0;
}
diff --git a/src/util/virutil.c b/src/util/virutil.c
index 311cbbf93a..8715deaca5 100644
--- a/src/util/virutil.c
+++ b/src/util/virutil.c
@@ -1936,3 +1936,92 @@ virPipeNonBlock(int fds[2])
{
return virPipeImpl(fds, true, true);
}
+
+int
+virGetDebugFsKvmValue(struct dirent *ent,
+ const char *path,
+ const char *filename,
+ unsigned long long *value)
+{
+ g_autofree char *valToStr = NULL;
+ g_autofree char *valPath = NULL;
+ int rc = -1;
+ int ret = -1;
+
+ valPath = g_strdup_printf("%s/%s/%s", path, ent->d_name, filename);
+
+ if ((rc = virFileReadAll(valPath, 16, &valToStr)) < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Unable to read from '%s'"), valPath);
+ goto cleanup;
+ }
+
+ /* Terminated with '\n' has sometimes harmful effects to the caller */
+ if (rc > 0 && (valToStr)[rc - 1] == '\n')
+ (valToStr)[rc - 1] = '\0';
+
+ /* 10 is a Cardinality, must be between 2 and 36 inclusive,
+ * or special value 0. Used in fuction strtoull()
+ */
+ if (virStrToLong_ull(valToStr, NULL, 10, value) < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Unable to parse '%s' as an integer"), valToStr);
+ goto cleanup;
+ }
+
+ ret = 0;
+cleanup:
+ return ret;
+}
+
+int
+virGetCpuHaltPollTime(pid_t pid,
+ unsigned long long *haltPollSuccess,
+ unsigned long long *haltPollFail)
+{
+ g_autofree char *pidToStr = NULL;
+ g_autofree char *debugFsPath = NULL;
+ g_autofree char *completePath = NULL;
+ struct dirent *ent = NULL;
+ DIR *dir = NULL;
+ int ret = -1;
+ int flag = 0;
+
+ if (!(debugFsPath = virFileFindMountPoint("debugfs"))) {
+ virReportSystemError(errno, "%s",
+ _("unable to find debugfs mountpoint"));
+ goto cleanup;
+ }
+
+ completePath = g_strdup_printf("%s/%s", debugFsPath, "kvm");
+ if (virDirOpen(&dir, completePath) < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ "%s %s", "Can not open directory", completePath);
+ return ret;
+ }
+
+ pidToStr = g_strdup_printf("%d", pid);
+ while (virDirRead(dir, &ent, NULL) > 0) {
+ if (strncmp(ent->d_name, pidToStr, strlen(pidToStr)) == 0 &&
+ ent->d_name[strlen(pidToStr)] == '-') {
+ flag = 1;
+ break;
+ }
+ }
+
+ if (flag == 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Could not find VM(Pid %s) in '%s'"), pidToStr, completePath);
+ goto cleanup;
+ }
+
+ if (virGetDebugFsKvmValue(ent, completePath, "halt_poll_success_ns", haltPollSuccess) < 0 ||
+ virGetDebugFsKvmValue(ent, completePath, "halt_poll_fail_ns", haltPollFail) < 0) {
+ goto cleanup;
+ }
+
+ ret = 0;
+cleanup:
+ closedir(dir);
+ return ret;
+}
diff --git a/src/util/virutil.h b/src/util/virutil.h
index 854b494890..b3c1e8a0bc 100644
--- a/src/util/virutil.h
+++ b/src/util/virutil.h
@@ -225,3 +225,12 @@ int virPipeQuiet(int fds[2]);
* Returns: -1 on error, 0 on success
*/
int virPipeNonBlock(int fds[2]);
+
+int virGetDebugFsKvmValue(struct dirent *ent,
+ const char *path,
+ const char *filename,
+ unsigned long long *value);
+
+int virGetCpuHaltPollTime(pid_t pid,
+ unsigned long long *haltPollSuccess,
+ unsigned long long *haltPollFail);
--
2.23.0
