diff options
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 8 | ||||
| -rw-r--r-- | include/linux/cgroup-defs.h | 21 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 2 | ||||
| -rw-r--r-- | init/Kconfig | 10 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup-internal.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 17 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup.c | 136 | ||||
| -rw-r--r-- | kernel/sched/psi.c | 19 |
8 files changed, 151 insertions, 63 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 176298f2f4de..bf842b80bde9 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -184,6 +184,14 @@ cgroup v2 currently supports the following mount options. ignored on non-init namespace mounts. Please refer to the Delegation section for details. + favordynmods + Reduce the latencies of dynamic cgroup modifications such as + task migrations and controller on/offs at the cost of making + hot path operations such as forks and exits more expensive. + The static usage pattern of creating a cgroup, enabling + controllers, and then seeding it with CLONE_INTO_CGROUP is + not affected by this option. + memory_localevents Only populate memory.events with data for the current cgroup, and not any subtrees. This is legacy behaviour, the default diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 187b54a9567e..4bcf56b3491c 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -89,19 +89,32 @@ enum { CGRP_ROOT_NS_DELEGATE = (1 << 3), /* + * Reduce latencies on dynamic cgroup modifications such as task + * migrations and controller on/offs by disabling percpu operation on + * cgroup_threadgroup_rwsem. This makes hot path operations such as + * forks and exits into the slow path and more expensive. + * + * The static usage pattern of creating a cgroup, enabling controllers, + * and then seeding it with CLONE_INTO_CGROUP doesn't require write + * locking cgroup_threadgroup_rwsem and thus doesn't benefit from + * favordynmod. + */ + CGRP_ROOT_FAVOR_DYNMODS = (1 << 4), + + /* * Enable cpuset controller in v1 cgroup to use v2 behavior. */ - CGRP_ROOT_CPUSET_V2_MODE = (1 << 4), + CGRP_ROOT_CPUSET_V2_MODE = (1 << 16), /* * Enable legacy local memory.events. */ - CGRP_ROOT_MEMORY_LOCAL_EVENTS = (1 << 5), + CGRP_ROOT_MEMORY_LOCAL_EVENTS = (1 << 17), /* * Enable recursive subtree protection */ - CGRP_ROOT_MEMORY_RECURSIVE_PROT = (1 << 6), + CGRP_ROOT_MEMORY_RECURSIVE_PROT = (1 << 18), }; /* cftype->flags */ @@ -480,7 +493,7 @@ struct cgroup { struct work_struct release_agent_work; /* used to track pressure stalls */ - struct psi_group psi; + struct psi_group *psi; /* used to store eBPF programs */ struct cgroup_bpf bpf; diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 0d1ada8968d7..ed53bfe7c46c 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -674,7 +674,7 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp) static inline struct psi_group *cgroup_psi(struct cgroup *cgrp) { - return &cgrp->psi; + return cgrp->psi; } bool cgroup_psi_enabled(void); diff --git a/init/Kconfig b/init/Kconfig index 26a544112732..8c9ad53b45dc 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -945,6 +945,16 @@ if CGROUPS config PAGE_COUNTER bool +config CGROUP_FAVOR_DYNMODS + bool "Favor dynamic modification latency reduction by default" + help + This option enables the "favordynmods" mount option by default + which reduces the latencies of dynamic cgroup modifications such + as task migrations and controller on/offs at the cost of making + hot path operations such as forks and exits more expensive. + + Say N if unsure. + config MEMCG bool "Memory controller" select PAGE_COUNTER diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index 5da09c74228d..36b740cb3d59 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -233,6 +233,7 @@ void cgroup_kn_unlock(struct kernfs_node *kn); int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen, struct cgroup_namespace *ns); +void cgroup_favor_dynmods(struct cgroup_root *root, bool favor); void cgroup_free_root(struct cgroup_root *root); void init_cgroup_root(struct cgroup_fs_context *ctx); int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask); diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index afc6c0e9c966..2ade21b54dc4 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -875,6 +875,8 @@ static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_roo seq_puts(seq, ",xattr"); if (root->flags & CGRP_ROOT_CPUSET_V2_MODE) seq_puts(seq, ",cpuset_v2_mode"); + if (root->flags & CGRP_ROOT_FAVOR_DYNMODS) + seq_puts(seq, ",favordynmods"); spin_lock(&release_agent_path_lock); if (strlen(root->release_agent_path)) @@ -898,6 +900,8 @@ enum cgroup1_param { Opt_noprefix, Opt_release_agent, Opt_xattr, + Opt_favordynmods, + Opt_nofavordynmods, }; const struct fs_parameter_spec cgroup1_fs_parameters[] = { @@ -909,6 +913,8 @@ const struct fs_parameter_spec cgroup1_fs_parameters[] = { fsparam_flag ("noprefix", Opt_noprefix), fsparam_string("release_agent", Opt_release_agent), fsparam_flag ("xattr", Opt_xattr), + fsparam_flag ("favordynmods", Opt_favordynmods), + fsparam_flag ("nofavordynmods", Opt_nofavordynmods), {} }; @@ -960,6 +966,12 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) case Opt_xattr: ctx->flags |= CGRP_ROOT_XATTR; break; + case Opt_favordynmods: + ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS; + break; + case Opt_nofavordynmods: + ctx->flags &= ~CGRP_ROOT_FAVOR_DYNMODS; + break; case Opt_release_agent: /* Specifying two release agents is forbidden */ if (ctx->release_agent) @@ -1211,8 +1223,11 @@ static int cgroup1_root_to_use(struct fs_context *fc) init_cgroup_root(ctx); ret = cgroup_setup_root(root, ctx->subsys_mask); - if (ret) + if (!ret) + cgroup_favor_dynmods(root, ctx->flags & CGRP_ROOT_FAVOR_DYNMODS); + else cgroup_free_root(root); + return ret; } diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 13c8e91d7862..ffaccd6373f1 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -279,8 +279,6 @@ bool cgroup_ssid_enabled(int ssid) * * - When mounting an existing superblock, mount options should match. * - * - Remount is disallowed. - * * - rename(2) is disallowed. * * - "tasks" is removed. Everything should be at process granularity. Use @@ -1309,6 +1307,20 @@ struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root) return root_cgrp->root; } +void cgroup_favor_dynmods(struct cgroup_root *root, bool favor) +{ + bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS; + + /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */ + if (favor && !favoring) { + rcu_sync_enter(&cgroup_threadgroup_rwsem.rss); + root->flags |= CGRP_ROOT_FAVOR_DYNMODS; + } else if (!favor && favoring) { + rcu_sync_exit(&cgroup_threadgroup_rwsem.rss); + root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS; + } +} + static int cgroup_init_root_id(struct cgroup_root *root) { int id; @@ -1369,6 +1381,7 @@ static void cgroup_destroy_root(struct cgroup_root *root) cgroup_root_count--; } + cgroup_favor_dynmods(root, false); cgroup_exit_root_id(root); mutex_unlock(&cgroup_mutex); @@ -1378,6 +1391,31 @@ static void cgroup_destroy_root(struct cgroup_root *root) cgroup_free_root(root); } +static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset, + struct cgroup_root *root) +{ + struct cgroup *res_cgroup = NULL; + + if (cset == &init_css_set) { + res_cgroup = &root->cgrp; + } else if (root == &cgrp_dfl_root) { + res_cgroup = cset->dfl_cgrp; + } else { + struct cgrp_cset_link *link; + + list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { + struct cgroup *c = link->cgrp; + + if (c->root == root) { + res_cgroup = c; + break; + } + } + } + + return res_cgroup; +} + /* * look up cgroup associated with current task's cgroup namespace on the * specified hierarchy @@ -1393,22 +1431,8 @@ current_cgns_cgroup_from_root(struct cgroup_root *root) rcu_read_lock(); cset = current->nsproxy->cgroup_ns->root_cset; - if (cset == &init_css_set) { - res = &root->cgrp; - } else if (root == &cgrp_dfl_root) { - res = cset->dfl_cgrp; - } else { - struct cgrp_cset_link *link; - - list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { - struct cgroup *c = link->cgrp; + res = __cset_cgroup_from_root(cset, root); - if (c->root == root) { - res = c; - break; - } - } - } rcu_read_unlock(); BUG_ON(!res); @@ -1424,22 +1448,7 @@ static struct cgroup *cset_cgroup_from_root(struct css_set *cset, lockdep_assert_held(&cgroup_mutex); lockdep_assert_held(&css_set_lock); - if (cset == &init_css_set) { - res = &root->cgrp; - } else if (root == &cgrp_dfl_root) { - res = cset->dfl_cgrp; - } else { - struct cgrp_cset_link *link; - - list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { - struct cgroup *c = link->cgrp; - - if (c->root == root) { - res = c; - break; - } - } - } + res = __cset_cgroup_from_root(cset, root); BUG_ON(!res); return res; @@ -1866,6 +1875,7 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node, enum cgroup2_param { Opt_nsdelegate, + Opt_favordynmods, Opt_memory_localevents, Opt_memory_recursiveprot, nr__cgroup2_params @@ -1873,6 +1883,7 @@ enum cgroup2_param { static const struct fs_parameter_spec cgroup2_fs_parameters[] = { fsparam_flag("nsdelegate", Opt_nsdelegate), + fsparam_flag("favordynmods", Opt_favordynmods), fsparam_flag("memory_localevents", Opt_memory_localevents), fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot), {} @@ -1892,6 +1903,9 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param case Opt_nsdelegate: ctx->flags |= CGRP_ROOT_NS_DELEGATE; return 0; + case Opt_favordynmods: + ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS; + return 0; case Opt_memory_localevents: ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS; return 0; @@ -1910,6 +1924,9 @@ static void apply_cgroup_root_flags(unsigned int root_flags) else cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE; + cgroup_favor_dynmods(&cgrp_dfl_root, + root_flags & CGRP_ROOT_FAVOR_DYNMODS); + if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS) cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS; else @@ -1926,6 +1943,8 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root { if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) seq_puts(seq, ",nsdelegate"); + if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS) + seq_puts(seq, ",favordynmods"); if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS) seq_puts(seq, ",memory_localevents"); if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT) @@ -1976,7 +1995,8 @@ void init_cgroup_root(struct cgroup_fs_context *ctx) cgrp->root = root; init_cgroup_housekeeping(cgrp); - root->flags = ctx->flags; + /* DYNMODS must be modified through cgroup_favor_dynmods() */ + root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS; if (ctx->release_agent) strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX); if (ctx->name) @@ -2198,6 +2218,10 @@ static int cgroup_init_fs_context(struct fs_context *fc) put_user_ns(fc->user_ns); fc->user_ns = get_user_ns(ctx->ns->user_ns); fc->global = true; + +#ifdef CONFIG_CGROUP_FAVOR_DYNMODS + ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS; +#endif return 0; } @@ -2572,10 +2596,6 @@ int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp) if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp)) return -EOPNOTSUPP; - /* mixables don't care */ - if (cgroup_is_mixable(dst_cgrp)) - return 0; - /* * If @dst_cgrp is already or can become a thread root or is * threaded, it doesn't matter. @@ -2949,22 +2969,40 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) struct cgroup_subsys_state *d_css; struct cgroup *dsct; struct css_set *src_cset; + bool has_tasks; int ret; lockdep_assert_held(&cgroup_mutex); - percpu_down_write(&cgroup_threadgroup_rwsem); - /* look up all csses currently attached to @cgrp's subtree */ spin_lock_irq(&css_set_lock); cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { struct cgrp_cset_link *link; + /* + * As cgroup_update_dfl_csses() is only called by + * cgroup_apply_control(). The csses associated with the + * given cgrp will not be affected by changes made to + * its subtree_control file. We can skip them. + */ + if (dsct == cgrp) + continue; + list_for_each_entry(link, &dsct->cset_links, cset_link) cgroup_migrate_add_src(link->cset, dsct, &mgctx); } spin_unlock_irq(&css_set_lock); + /* + * We need to write-lock threadgroup_rwsem while migrating tasks. + * However, if there are no source csets for @cgrp, changing its + * controllers isn't gonna produce any task migrations and the + * write-locking can be skipped safely. + */ + has_tasks = !list_empty(&mgctx.preloaded_src_csets); + if (has_tasks) + percpu_down_write(&cgroup_threadgroup_rwsem); + /* NULL dst indicates self on default hierarchy */ ret = cgroup_migrate_prepare_dst(&mgctx); if (ret) @@ -2984,7 +3022,8 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) ret = cgroup_migrate_execute(&mgctx); out_finish: cgroup_migrate_finish(&mgctx); - percpu_up_write(&cgroup_threadgroup_rwsem); + if (has_tasks) + percpu_up_write(&cgroup_threadgroup_rwsem); return ret; } @@ -3618,21 +3657,21 @@ static int cpu_stat_show(struct seq_file *seq, void *v) static int cgroup_io_pressure_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; - struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; + struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi; return psi_show(seq, psi, PSI_IO); } static int cgroup_memory_pressure_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; - struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; + struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi; return psi_show(seq, psi, PSI_MEM); } static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; - struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; + struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi; return psi_show(seq, psi, PSI_CPU); } @@ -3658,7 +3697,7 @@ static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf, return -EBUSY; } - psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; + psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi; new = psi_trigger_create(psi, buf, nbytes, res); if (IS_ERR(new)) { cgroup_put(cgrp); @@ -5851,12 +5890,6 @@ int __init cgroup_init(void) cgroup_rstat_boot(); - /* - * The latency of the synchronize_rcu() is too high for cgroups, - * avoid it at the cost of forcing all readers into the slow path. - */ - rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss); - get_user_ns(init_cgroup_ns.user_ns); mutex_lock(&cgroup_mutex); @@ -6768,6 +6801,7 @@ static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr, { return snprintf(buf, PAGE_SIZE, "nsdelegate\n" + "favordynmods\n" "memory_localevents\n" "memory_recursiveprot\n"); } diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index a337f3e35997..ec66b40bdd40 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -957,10 +957,16 @@ int psi_cgroup_alloc(struct cgroup *cgroup) if (static_branch_likely(&psi_disabled)) return 0; - cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu); - if (!cgroup->psi.pcpu) + cgroup->psi = kmalloc(sizeof(struct psi_group), GFP_KERNEL); + if (!cgroup->psi) return -ENOMEM; - group_init(&cgroup->psi); + + cgroup->psi->pcpu = alloc_percpu(struct psi_group_cpu); + if (!cgroup->psi->pcpu) { + kfree(cgroup->psi); + return -ENOMEM; + } + group_init(cgroup->psi); return 0; } @@ -969,10 +975,11 @@ void psi_cgroup_free(struct cgroup *cgroup) if (static_branch_likely(&psi_disabled)) return; - cancel_delayed_work_sync(&cgroup->psi.avgs_work); - free_percpu(cgroup->psi.pcpu); + cancel_delayed_work_sync(&cgroup->psi->avgs_work); + free_percpu(cgroup->psi->pcpu); /* All triggers must be removed by now */ - WARN_ONCE(cgroup->psi.poll_states, "psi: trigger leak\n"); + WARN_ONCE(cgroup->psi->poll_states, "psi: trigger leak\n"); + kfree(cgroup->psi); } /** |