In order to set CPU cfs period using cgroup v2 'cpu.max' interface
we need to load the current value of CPU cfs quota first because
format of 'cpu.max' interface is '$quota $period' and in order to
change 'period' we need to write 'quota' as well.  Writing only one
number changes only 'quota'.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
---
 src/util/vircgroupv2.c | 68 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
index 986b2d07c1..24c5bb3e3d 100644
--- a/src/util/vircgroupv2.c
+++ b/src/util/vircgroupv2.c
@@ -1333,6 +1333,72 @@ virCgroupV2GetCpuShares(virCgroupPtr group,
 }
 
 
+static int
+virCgroupV2SetCpuCfsPeriod(virCgroupPtr group,
+                           unsigned long long cfs_period)
+{
+    VIR_AUTOFREE(char *) value = NULL;
+    VIR_AUTOFREE(char *) str = NULL;
+    char *tmp;
+
+    /* The cfs_period should be greater or equal than 1ms, and less or equal
+     * than 1s.
+     */
+    if (cfs_period < 1000 || cfs_period > 1000000) {
+        virReportError(VIR_ERR_INVALID_ARG,
+                       _("cfs_period '%llu' must be in range (1000, 1000000)"),
+                       cfs_period);
+        return -1;
+    }
+
+    if (virCgroupGetValueStr(group, VIR_CGROUP_CONTROLLER_CPU,
+                             "cpu.max", &str) < 0) {
+        return -1;
+    }
+
+    if (!(tmp = strchr(str, ' '))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Invalid 'cpu.max' data."));
+        return -1;
+    }
+    *tmp = '\n';
+
+    if (virAsprintf(&value, "%s %llu", str, cfs_period) < 0)
+        return -1;
+
+    return virCgroupSetValueStr(group, VIR_CGROUP_CONTROLLER_CPU,
+                                "cpu.max", value);
+}
+
+
+static int
+virCgroupV2GetCpuCfsPeriod(virCgroupPtr group,
+                           unsigned long long *cfs_period)
+{
+    VIR_AUTOFREE(char *) str = NULL;
+    char *tmp;
+
+    if (virCgroupGetValueStr(group, VIR_CGROUP_CONTROLLER_CPU,
+                             "cpu.max", &str) < 0) {
+        return -1;
+    }
+
+    if (!(tmp = strchr(str, ' '))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Invalid 'cpu.max' data."));
+        return -1;
+    }
+
+    if (virStrToLong_ull(tmp, NULL, 10, cfs_period) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Failed to parse value '%s' from cpu.max."), str);
+        return -1;
+    }
+
+    return 0;
+}
+
+
 virCgroupBackend virCgroupV2Backend = {
     .type = VIR_CGROUP_BACKEND_TYPE_V2,
 
@@ -1383,6 +1449,8 @@ virCgroupBackend virCgroupV2Backend = {
 
     .setCpuShares = virCgroupV2SetCpuShares,
     .getCpuShares = virCgroupV2GetCpuShares,
+    .setCpuCfsPeriod = virCgroupV2SetCpuCfsPeriod,
+    .getCpuCfsPeriod = virCgroupV2GetCpuCfsPeriod,
 };
 
 
-- 
2.17.1

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