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cgroup/pids: Add pids.events.local

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Hierarchical counting of events is not practical for watching when a
particular pids.max is being hit. Therefore introduce .local flavor of
events file (akin to memory controller) that collects only events
relevant to given cgroup.

The file is only added to the default hierarchy.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Michal Koutný 2024-05-21 11:21:28 +02:00 committed by Tejun Heo
parent 385a635cac
commit 3f26a885a0
2 changed files with 76 additions and 18 deletions
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5
Documentation/admin-guide/cgroup-v2.rst
View File

@ -2220,6 +2220,11 @@ PID Interface Files
The number of times the cgroup's total number of processes hit the pids.max
limit (see also pids_localevents).
pids.events.local
Similar to pids.events but the fields in the file are local
to the cgroup i.e. not hierarchical. The file modified event
generated on this file reflects only the local events.
Organisational operations are not blocked by cgroup policies, so it is
possible to have pids.current > pids.max. This can be done by either
setting the limit to be smaller than pids.current, or attaching enough

89
kernel/cgroup/pids.c
View File

@ -57,10 +57,12 @@ struct pids_cgroup {
atomic64_t limit;
int64_t watermark;
/* Handle for "pids.events" */
/* Handles for pids.events[.local] */
struct cgroup_file events_file;
struct cgroup_file events_local_file;
atomic64_t events[NR_PIDCG_EVENTS];
atomic64_t events_local[NR_PIDCG_EVENTS];
};
static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
@ -244,21 +246,23 @@ static void pids_event(struct pids_cgroup *pids_forking,
struct pids_cgroup *p = pids_forking;
bool limit = false;
/* Only log the first time limit is hit. */
if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
pr_info("cgroup: fork rejected by pids controller in ");
pr_cont_cgroup_path(p->css.cgroup);
pr_cont("\n");
}
cgroup_file_notify(&p->events_local_file);
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
return;
for (; parent_pids(p); p = parent_pids(p)) {
/* Only log the first time limit is hit. */
if (atomic64_inc_return(&p->events[PIDCG_FORKFAIL]) == 1) {
pr_info("cgroup: fork rejected by pids controller in ");
pr_cont_cgroup_path(p->css.cgroup);
pr_cont("\n");
}
cgroup_file_notify(&p->events_file);
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
break;
if (p == pids_over_limit)
if (p == pids_over_limit) {
limit = true;
atomic64_inc(&p->events_local[PIDCG_MAX]);
cgroup_file_notify(&p->events_local_file);
}
if (limit)
atomic64_inc(&p->events[PIDCG_MAX]);
@ -368,16 +372,32 @@ static s64 pids_peak_read(struct cgroup_subsys_state *css,
return READ_ONCE(pids->watermark);
}
static int pids_events_show(struct seq_file *sf, void *v)
static int __pids_events_show(struct seq_file *sf, bool local)
{
struct pids_cgroup *pids = css_pids(seq_css(sf));
enum pidcg_event pe = PIDCG_MAX;
atomic64_t *events;
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
pe = PIDCG_FORKFAIL;
local = true;
}
events = local ? pids->events_local : pids->events;
seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events[pe]));
seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe]));
return 0;
}
static int pids_events_show(struct seq_file *sf, void *v)
{
__pids_events_show(sf, false);
return 0;
}
static int pids_events_local_show(struct seq_file *sf, void *v)
{
__pids_events_show(sf, true);
return 0;
}
@ -404,9 +424,42 @@ static struct cftype pids_files[] = {
.file_offset = offsetof(struct pids_cgroup, events_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "events.local",
.seq_show = pids_events_local_show,
.file_offset = offsetof(struct pids_cgroup, events_local_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{ } /* terminate */
};
static struct cftype pids_files_legacy[] = {
{
.name = "max",
.write = pids_max_write,
.seq_show = pids_max_show,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "current",
.read_s64 = pids_current_read,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "peak",
.flags = CFTYPE_NOT_ON_ROOT,
.read_s64 = pids_peak_read,
},
{
.name = "events",
.seq_show = pids_events_show,
.file_offset = offsetof(struct pids_cgroup, events_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{ } /* terminate */
};
struct cgroup_subsys pids_cgrp_subsys = {
.css_alloc = pids_css_alloc,
.css_free = pids_css_free,
@ -415,7 +468,7 @@ struct cgroup_subsys pids_cgrp_subsys = {
.can_fork = pids_can_fork,
.cancel_fork = pids_cancel_fork,
.release = pids_release,
.legacy_cftypes = pids_files,
.legacy_cftypes = pids_files_legacy,
.dfl_cftypes = pids_files,
.threaded = true,
};