From: Tejun Heo <[email protected]> Now that cpu serves the same files as cpuacct and using cpuacct separately from cpu is deprecated, we can deprecate cpuacct. To avoid disturbing userland which has been co-mounting cpu and cpuacct, implement some hackery in cgroup core so that cpuacct co-mounting still works even if cpuacct is disabled.
The goal of this patch is to accelerate disabling and removal of cpuacct by decoupling kernel-side deprecation from userland changes. Userland is recommended to do the following. * If /proc/cgroups lists cpuacct, always co-mount it with cpu under e.g. /sys/fs/cgroup/cpu. * Optionally create symlinks for compatibility - e.g. /sys/fs/cgroup/cpuacct and /sys/fs/cgroup/cpu,cpucct both pointing to /sys/fs/cgroup/cpu - whether cpuacct exists or not. This compatibility hack will eventually go away. [ [email protected]: subsys_bits => subsys_mask ] Signed-off-by: Tejun Heo <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Glauber Costa <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Kay Sievers <[email protected]> Cc: Lennart Poettering <[email protected]> Cc: Dave Jones <[email protected]> Cc: Ben Hutchings <[email protected]> Cc: Paul Turner <[email protected]> --- init/Kconfig | 11 ++++++++++- kernel/cgroup.c | 47 ++++++++++++++++++++++++++++++++++++++++++----- kernel/sched/core.c | 2 ++ 3 files changed, 54 insertions(+), 6 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 7d30240..4e411ac 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -815,11 +815,20 @@ config PROC_PID_CPUSET default y config CGROUP_CPUACCT - bool "Simple CPU accounting cgroup subsystem" + bool "DEPRECATED: Simple CPU accounting cgroup subsystem" + default n help Provides a simple Resource Controller for monitoring the total CPU consumed by the tasks in a cgroup. + This cgroup subsystem is deprecated. The CPU cgroup + subsystem serves the same accounting files and "cpuacct" + mount option is ignored if specified with "cpu". As long as + userland co-mounts cpu and cpuacct, disabling this + controller should be mostly unnoticeable - one notable + difference is that /proc/PID/cgroup won't list cpuacct + anymore. + config RESOURCE_COUNTERS bool "Resource counters" help diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0750669d..4ddb335 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1136,6 +1136,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) unsigned long mask = (unsigned long)-1; int i; bool module_pin_failed = false; + bool cpuacct_requested = false; BUG_ON(!mutex_is_locked(&cgroup_mutex)); @@ -1225,8 +1226,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) break; } - if (i == CGROUP_SUBSYS_COUNT) + /* handle deprecated cpuacct specially, see below */ + if (!strcmp(token, "cpuacct")) { + cpuacct_requested = true; + one_ss = true; + } else if (i == CGROUP_SUBSYS_COUNT) { return -ENOENT; + } } /* @@ -1253,12 +1259,29 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) * this creates some discrepancies in /proc/cgroups and * /proc/PID/cgroup. * + * Accept and ignore "cpuacct" option if comounted with "cpu" even + * when cpuacct itself is disabled to allow quick disabling and + * removal of cpuacct. This will be removed eventually. + * * https://lkml.org/lkml/2012/9/13/542 */ + if (cpuacct_requested) { + bool comounted = false; + +#if IS_ENABLED(CONFIG_CGROUP_SCHED) + comounted = opts->subsys_mask & (1 << cpu_cgroup_subsys_id); +#endif + if (!comounted) { + pr_warning("cgroup: mounting cpuacct separately from cpu is deprecated\n"); +#if !IS_ENABLED(CONFIG_CGROUP_CPUACCT) + return -EINVAL; +#endif + } + } #if IS_ENABLED(CONFIG_CGROUP_SCHED) && IS_ENABLED(CONFIG_CGROUP_CPUACCT) - if ((opts->subsys_bits & (1 << cpu_cgroup_subsys_id)) && - (opts->subsys_bits & (1 << cpuacct_subsys_id))) - opts->subsys_bits &= ~(1 << cpuacct_subsys_id); + if ((opts->subsys_mask & (1 << cpu_cgroup_subsys_id)) && + (opts->subsys_mask & (1 << cpuacct_subsys_id))) + opts->subsys_mask &= ~(1 << cpuacct_subsys_id); #endif /* * Option noprefix was introduced just for backward compatibility @@ -4806,6 +4829,7 @@ const struct file_operations proc_cgroup_operations = { /* Display information about each subsystem and each hierarchy */ static int proc_cgroupstats_show(struct seq_file *m, void *v) { + struct cgroup_subsys *ss; int i; seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n"); @@ -4816,7 +4840,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v) */ mutex_lock(&cgroup_mutex); for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { - struct cgroup_subsys *ss = subsys[i]; + ss = subsys[i]; if (ss == NULL) continue; seq_printf(m, "%s\t%d\t%d\t%d\n", @@ -4824,6 +4848,19 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v) ss->root->number_of_cgroups, !ss->disabled); } mutex_unlock(&cgroup_mutex); + + /* + * Fake /proc/cgroups entry for cpuacct to trick userland into + * cpu,cpuacct comounts. This is to allow quick disabling and + * removal of cpuacct and will be removed eventually. + */ +#if IS_ENABLED(CONFIG_CGROUP_SCHED) && !IS_ENABLED(CONFIG_CGROUP_CPUACCT) + ss = subsys[cpu_cgroup_subsys_id]; + if (ss) { + seq_printf(m, "cpuacct\t%d\t%d\t%d\n", ss->root->hierarchy_id, + ss->root->number_of_cgroups, !ss->disabled); + } +#endif return 0; } diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6516694..a62b771 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8110,6 +8110,8 @@ struct cgroup_subsys cpu_cgroup_subsys = { #ifdef CONFIG_CGROUP_CPUACCT +#warning CONFIG_CGROUP_CPUACCT is deprecated, read the Kconfig help message + /* * CPU accounting code for task groups. * -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
