7:55 a.m.
On 10/02/2018 10:43 AM, Pavel Hrdina wrote:
When creating cgroup hierarchy we need to enable controllers in the
parent cgroup in order to be usable. That means writing "+{controller}"
into cgroup.subtree_control file. We can enable only controllers that
are enabled for parent cgroup, that means we need to do that for the
whole cgroup tree.
Cgroups for threads needs to be handled differently in cgroup v2. There
are two types of controllers:
- domain controllers: these cannot be enabled for threads
- threaded controllers: these can be enabled for threads
In addition there are multiple types of cgroups:
- domain: normal cgroup
- domain threaded: a domain cgroup that serves as root for threaded
cgroups
- domain invalid: invalid cgroup, can be changed into threaded, this
is the default state if you create subgroup inside
domain threaded group or threaded group
- threaded: threaded cgroup which can have domain threaded or
threaded as parent group
In order to create threaded cgroup it's sufficient to write "threaded"
into cgroup.type file, it will automatically make parent cgroup
"domain threaded" if it was only "domain". In case the parent
cgroup
is already "domain threaded" or "threaded" it will modify only the
type
of current cgroup. After that we can enable threaded controllers.
Signed-off-by: Pavel Hrdina <phrdina(a)redhat.com>
---
src/util/vircgroup.c | 2 +-
src/util/vircgroupbackend.h | 1 +
src/util/vircgroupv2.c | 78 +++++++++++++++++++++++++++++++++++++
3 files changed, 80 insertions(+), 1 deletion(-)
diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index 1097b1f998..dc249bfe33 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -938,7 +938,7 @@ virCgroupNewThread(virCgroupPtr domain,
if (virCgroupNew(-1, name, domain, controllers, group) < 0)
return -1;
- if (virCgroupMakeGroup(domain, *group, create, VIR_CGROUP_NONE) < 0) {
+ if (virCgroupMakeGroup(domain, *group, create, VIR_CGROUP_THREAD) < 0) {
So unsupported flags are ignored?
virCgroupFree(group);
return -1;
}
diff --git a/src/util/vircgroupbackend.h b/src/util/vircgroupbackend.h
index b1f19233e4..86d1539e07 100644
--- a/src/util/vircgroupbackend.h
+++ b/src/util/vircgroupbackend.h
@@ -33,6 +33,7 @@ typedef enum {
* before creating subcgroups and
* attaching tasks
*/
+ VIR_CGROUP_THREAD = 1 << 1, /* cgroup v2 handles threads differently */
} virCgroupBackendFlags;
typedef enum {
diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
index 3ca463e4c2..8fb9ace474 100644
--- a/src/util/vircgroupv2.c
+++ b/src/util/vircgroupv2.c
@@ -336,6 +336,83 @@ virCgroupV2PathOfController(virCgroupPtr group,
}
+static int
+virCgroupV2EnableController(virCgroupPtr parent,
+ int controller)
+{
+ VIR_AUTOFREE(char *) val = NULL;
+
+ if (virAsprintf(&val, "+%s",
+ virCgroupV2ControllerTypeToString(controller)) < 0) {
+ return -1;
+ }
+
+ if (virCgroupSetValueStr(parent, controller,
+ "cgroup.subtree_control", val) < 0) {
+ return -1;
+ }
+
+ return 0;
+}
+
+
+static int
+virCgroupV2MakeGroup(virCgroupPtr parent ATTRIBUTE_UNUSED,
+ virCgroupPtr group,
+ bool create,
+ unsigned int flags)
+{
+ VIR_AUTOFREE(char *) path = NULL;
+ int controller;
+
+ VIR_DEBUG("Make group %s", group->path);
+
+ controller = virCgroupV2GetAnyController(group);
+ if (virCgroupV2PathOfController(group, controller, "", &path) < 0)
+ return -1;
+
+ VIR_DEBUG("Make controller %s", path);
+
+ if (!virFileExists(path)) {
This should have been virFileIsDir() because EEXIST doesn't mean the
@path is a directory. It could be a regular file.
+ if (!create || mkdir(path, 0755 || errno == EEXIST) < 0)
{
Ooops, misplaced ')'. mkdir() || errno ;-) This is why I tend to write
each condition on a separate line. But if you want to ignore EEXIST then
you need to rewrite this check as follows:
if (!create || (mkdir() < 0 && errno != EEXIST))
However, I don't think you want to ignore any errno.
Also, any reason these two if()-s should not be merged into one?
+ virReportSystemError(errno,
+ _("Failed to create v2 cgroup
'%s'"),
+ group->path);
+ return -1;
+ }
+ }
+
+ if (create) {
+ if (flags & VIR_CGROUP_THREAD) {
+ if (virCgroupSetValueStr(group, VIR_CGROUP_CONTROLLER_CPU,
+ "cgroup.type", "threaded") <
0) {
+ return -1;
+ }
+
+ if (virCgroupV2EnableController(parent,
+ VIR_CGROUP_CONTROLLER_CPU) < 0) {
+ return -1;
+ }
+ } else {
+ size_t i;
+ for (i = 0; i < VIR_CGROUP_CONTROLLER_LAST; i++) {
+ if (!virCgroupV2HasController(parent, i))
+ continue;
+
+ /* Controllers that are implicitly enabled if available. */
+ if (i == VIR_CGROUP_CONTROLLER_CPUACCT)
+ continue;
+
+ if (virCgroupV2EnableController(parent, i) < 0)
+ return -1;
+ }
+ }
+ }
+
+ return 0;
+}
+
+
virCgroupBackend virCgroupV2Backend = {
.type = VIR_CGROUP_BACKEND_TYPE_V2,
@@ -351,6 +428,7 @@ virCgroupBackend virCgroupV2Backend = {
.hasController = virCgroupV2HasController,
.getAnyController = virCgroupV2GetAnyController,
.pathOfController = virCgroupV2PathOfController,
+ .makeGroup = virCgroupV2MakeGroup,
};
Michal