diff options
author | Hao Jia <jiahao.os@bytedance.com> | 2023-08-07 11:29:30 +0800 |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2023-08-07 08:41:25 -1000 |
commit | 0437719c1a97791481c5fd59642494f2108701a8 (patch) | |
tree | bfcf3316cae8af8e104241529ba6feb9646d7740 /kernel/cgroup | |
parent | e7e64a1bff12f212be12b048723718c2152c4489 (diff) |
cgroup/rstat: Record the cumulative per-cpu time of cgroup and its descendants
The member variable bstat of the structure cgroup_rstat_cpu
records the per-cpu time of the cgroup itself, but does not
include the per-cpu time of its descendants. The per-cpu time
including descendants is very useful for calculating the
per-cpu usage of cgroups.
Although we can indirectly obtain the total per-cpu time
of the cgroup and its descendants by accumulating the per-cpu
bstat of each descendant of the cgroup. But after a child cgroup
is removed, we will lose its bstat information. This will cause
the cumulative value to be non-monotonic, thus affecting
the accuracy of cgroup per-cpu usage.
So we add the subtree_bstat variable to record the total
per-cpu time of this cgroup and its descendants, which is
similar to "cpuacct.usage*" in cgroup v1. And this is
also helpful for the migration from cgroup v1 to cgroup v2.
After adding this variable, we can obtain the per-cpu time of
cgroup and its descendants in user mode through eBPF/drgn, etc.
And we are still trying to determine how to expose it in the
cgroupfs interface.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r-- | kernel/cgroup/rstat.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index 2542c21b6b6d..d80d7a608141 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -344,6 +344,7 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu) { struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu); struct cgroup *parent = cgroup_parent(cgrp); + struct cgroup_rstat_cpu *prstatc; struct cgroup_base_stat delta; unsigned seq; @@ -357,17 +358,24 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu) delta = rstatc->bstat; } while (__u64_stats_fetch_retry(&rstatc->bsync, seq)); - /* propagate percpu delta to global */ + /* propagate per-cpu delta to cgroup and per-cpu global statistics */ cgroup_base_stat_sub(&delta, &rstatc->last_bstat); cgroup_base_stat_add(&cgrp->bstat, &delta); cgroup_base_stat_add(&rstatc->last_bstat, &delta); + cgroup_base_stat_add(&rstatc->subtree_bstat, &delta); - /* propagate global delta to parent (unless that's root) */ + /* propagate cgroup and per-cpu global delta to parent (unless that's root) */ if (cgroup_parent(parent)) { delta = cgrp->bstat; cgroup_base_stat_sub(&delta, &cgrp->last_bstat); cgroup_base_stat_add(&parent->bstat, &delta); cgroup_base_stat_add(&cgrp->last_bstat, &delta); + + delta = rstatc->subtree_bstat; + prstatc = cgroup_rstat_cpu(parent, cpu); + cgroup_base_stat_sub(&delta, &rstatc->last_subtree_bstat); + cgroup_base_stat_add(&prstatc->subtree_bstat, &delta); + cgroup_base_stat_add(&rstatc->last_subtree_bstat, &delta); } } |