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authorTejun Heo <htejun@fb.com>2016-08-15 18:13:36 -0400
committerTejun Heo <tj@kernel.org>2016-08-17 17:44:36 -0400
commit5da38d0768bf53f611ccdd47d7d941e1c560e44e (patch)
tree73ab0b904fca6a1e08e4904467efb82be01d4d06 /src/core/cgroup.c
parentca2f6384aa2076576b316c7253964be90b102d96 (diff)
core: use the unified hierarchy for the systemd cgroup controller hierarchy
Currently, systemd uses either the legacy hierarchies or the unified hierarchy. When the legacy hierarchies are used, systemd uses a named legacy hierarchy mounted on /sys/fs/cgroup/systemd without any kernel controllers for process management. Due to the shortcomings in the legacy hierarchy, this involves a lot of workarounds and complexities. Because the unified hierarchy can be mounted and used in parallel to legacy hierarchies, there's no reason for systemd to use a legacy hierarchy for management even if the kernel resource controllers need to be mounted on legacy hierarchies. It can simply mount the unified hierarchy under /sys/fs/cgroup/systemd and use it without affecting other legacy hierarchies. This disables a significant amount of fragile workaround logics and would allow using features which depend on the unified hierarchy membership such bpf cgroup v2 membership test. In time, this would also allow deleting the said complexities. This patch updates systemd so that it prefers the unified hierarchy for the systemd cgroup controller hierarchy when legacy hierarchies are used for kernel resource controllers. * cg_unified(@controller) is introduced which tests whether the specific controller in on unified hierarchy and used to choose the unified hierarchy code path for process and service management when available. Kernel controller specific operations remain gated by cg_all_unified(). * "systemd.legacy_systemd_cgroup_controller" kernel argument can be used to force the use of legacy hierarchy for systemd cgroup controller. * nspawn: By default nspawn uses the same hierarchies as the host. If UNIFIED_CGROUP_HIERARCHY is set to 1, unified hierarchy is used for all. If 0, legacy for all. * nspawn: arg_unified_cgroup_hierarchy is made an enum and now encodes one of three options - legacy, only systemd controller on unified, and unified. The value is passed into mount setup functions and controls cgroup configuration. * nspawn: Interpretation of SYSTEMD_CGROUP_CONTROLLER to the actual mount option is moved to mount_legacy_cgroup_hierarchy() so that it can take an appropriate action depending on the configuration of the host. v2: - CGroupUnified enum replaces open coded integer values to indicate the cgroup operation mode. - Various style updates. v3: Fixed a bug in detect_unified_cgroup_hierarchy() introduced during v2. v4: Restored legacy container on unified host support and fixed another bug in detect_unified_cgroup_hierarchy().
Diffstat (limited to 'src/core/cgroup.c')
-rw-r--r--src/core/cgroup.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 7c6fc01c0e..4b73a9ac13 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1245,7 +1245,7 @@ int unit_watch_cgroup(Unit *u) {
return 0;
/* Only applies to the unified hierarchy */
- r = cg_all_unified();
+ r = cg_unified(SYSTEMD_CGROUP_CONTROLLER);
if (r < 0)
return log_unit_error_errno(u, r, "Failed detect whether the unified hierarchy is used: %m");
if (r == 0)
@@ -1645,7 +1645,7 @@ int unit_watch_all_pids(Unit *u) {
if (!u->cgroup_path)
return -ENOENT;
- if (cg_all_unified() > 0) /* On unified we can use proper notifications */
+ if (cg_unified(SYSTEMD_CGROUP_CONTROLLER) > 0) /* On unified we can use proper notifications */
return 0;
return unit_watch_pids_in_path(u, u->cgroup_path);
@@ -1718,7 +1718,7 @@ static int on_cgroup_inotify_event(sd_event_source *s, int fd, uint32_t revents,
int manager_setup_cgroup(Manager *m) {
_cleanup_free_ char *path = NULL;
CGroupController c;
- int r, unified;
+ int r, all_unified, systemd_unified;
char *e;
assert(m);
@@ -1755,11 +1755,17 @@ int manager_setup_cgroup(Manager *m) {
if (r < 0)
return log_error_errno(r, "Cannot find cgroup mount point: %m");
- unified = cg_all_unified();
- if (unified < 0)
- return log_error_errno(r, "Couldn't determine if we are running in the unified hierarchy: %m");
- if (unified > 0)
+ all_unified = cg_all_unified();
+ systemd_unified = cg_unified(SYSTEMD_CGROUP_CONTROLLER);
+
+ if (all_unified < 0 || systemd_unified < 0)
+ return log_error_errno(all_unified < 0 ? all_unified : systemd_unified,
+ "Couldn't determine if we are running in the unified hierarchy: %m");
+
+ if (all_unified > 0)
log_debug("Unified cgroup hierarchy is located at %s.", path);
+ else if (systemd_unified > 0)
+ log_debug("Unified cgroup hierarchy is located at %s. Controllers are on legacy hierarchies.", path);
else
log_debug("Using cgroup controller " SYSTEMD_CGROUP_CONTROLLER ". File system hierarchy is at %s.", path);
@@ -1767,7 +1773,7 @@ int manager_setup_cgroup(Manager *m) {
const char *scope_path;
/* 3. Install agent */
- if (unified) {
+ if (systemd_unified) {
/* In the unified hierarchy we can get
* cgroup empty notifications via inotify. */
@@ -1827,7 +1833,7 @@ int manager_setup_cgroup(Manager *m) {
return log_error_errno(errno, "Failed to open pin file: %m");
/* 6. Always enable hierarchical support if it exists... */
- if (!unified)
+ if (!all_unified)
(void) cg_set_attribute("memory", "/", "memory.use_hierarchy", "1");
}