kernel/cgroup/rstat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include "cgroup-internal.h"
   3
   4 #include <linux/sched/cputime.h>
   5
   6 static DEFINE_SPINLOCK(cgroup_rstat_lock);
   7 static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
   8
   9 static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu);
  10
  11 static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu)
  12 {
  13         return per_cpu_ptr(cgrp->rstat_cpu, cpu);
  14 }
  15
  16 /**
  17  * cgroup_rstat_updated - keep track of updated rstat_cpu
  18  * @cgrp: target cgroup
  19  * @cpu: cpu on which rstat_cpu was updated
  20  *
  21  * @cgrp's rstat_cpu on @cpu was updated.  Put it on the parent's matching
  22  * rstat_cpu->updated_children list.  See the comment on top of
  23  * cgroup_rstat_cpu definition for details.
  24  */
  25 void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
  26 {
  27         raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
  28         struct cgroup *parent;
  29         unsigned long flags;
  30
  31         /* nothing to do for root */
  32         if (!cgroup_parent(cgrp))
  33                 return;
  34
  35         /*
  36          * Speculative already-on-list test. This may race leading to
  37          * temporary inaccuracies, which is fine.
  38          *
  39          * Because @parent's updated_children is terminated with @parent
  40          * instead of NULL, we can tell whether @cgrp is on the list by
  41          * testing the next pointer for NULL.
  42          */
  43         if (cgroup_rstat_cpu(cgrp, cpu)->updated_next)
  44                 return;
  45
  46         raw_spin_lock_irqsave(cpu_lock, flags);
  47
  48         /* put @cgrp and all ancestors on the corresponding updated lists */
  49         for (parent = cgroup_parent(cgrp); parent;
  50              cgrp = parent, parent = cgroup_parent(cgrp)) {
  51                 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
  52                 struct cgroup_rstat_cpu *prstatc = cgroup_rstat_cpu(parent, cpu);
  53
  54                 /*
  55                  * Both additions and removals are bottom-up.  If a cgroup
  56                  * is already in the tree, all ancestors are.
  57                  */
  58                 if (rstatc->updated_next)
  59                         break;
  60
  61                 rstatc->updated_next = prstatc->updated_children;
  62                 prstatc->updated_children = cgrp;
  63         }
  64
  65         raw_spin_unlock_irqrestore(cpu_lock, flags);
  66 }
  67
  68 /**
  69  * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree
  70  * @pos: current position
  71  * @root: root of the tree to traversal
  72  * @cpu: target cpu
  73  *
  74  * Walks the udpated rstat_cpu tree on @cpu from @root.  %NULL @pos starts
  75  * the traversal and %NULL return indicates the end.  During traversal,
  76  * each returned cgroup is unlinked from the tree.  Must be called with the
  77  * matching cgroup_rstat_cpu_lock held.
  78  *
  79  * The only ordering guarantee is that, for a parent and a child pair
  80  * covered by a given traversal, if a child is visited, its parent is
  81  * guaranteed to be visited afterwards.
  82  */
  83 static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
  84                                                    struct cgroup *root, int cpu)
  85 {
  86         struct cgroup_rstat_cpu *rstatc;
  87
  88         if (pos == root)
  89                 return NULL;
  90
  91         /*
  92          * We're gonna walk down to the first leaf and visit/remove it.  We
  93          * can pick whatever unvisited node as the starting point.
  94          */
  95         if (!pos)
  96                 pos = root;
  97         else
  98                 pos = cgroup_parent(pos);
  99
 100         /* walk down to the first leaf */
 101         while (true) {
 102                 rstatc = cgroup_rstat_cpu(pos, cpu);
 103                 if (rstatc->updated_children == pos)
 104                         break;
 105                 pos = rstatc->updated_children;
 106         }
 107
 108         /*
 109          * Unlink @pos from the tree.  As the updated_children list is
 110          * singly linked, we have to walk it to find the removal point.
 111          * However, due to the way we traverse, @pos will be the first
 112          * child in most cases. The only exception is @root.
 113          */
 114         if (rstatc->updated_next) {
 115                 struct cgroup *parent = cgroup_parent(pos);
 116                 struct cgroup_rstat_cpu *prstatc = cgroup_rstat_cpu(parent, cpu);
 117                 struct cgroup_rstat_cpu *nrstatc;
 118                 struct cgroup **nextp;
 119
 120                 nextp = &prstatc->updated_children;
 121                 while (true) {
 122                         nrstatc = cgroup_rstat_cpu(*nextp, cpu);
 123                         if (*nextp == pos)
 124                                 break;
 125
 126                         WARN_ON_ONCE(*nextp == parent);
 127                         nextp = &nrstatc->updated_next;
 128                 }
 129
 130                 *nextp = rstatc->updated_next;
 131                 rstatc->updated_next = NULL;
 132
 133                 return pos;
 134         }
 135
 136         /* only happens for @root */
 137         return NULL;
 138 }
 139
 140 /* see cgroup_rstat_flush() */
 141 static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
 142         __releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
 143 {
 144         int cpu;
 145
 146         lockdep_assert_held(&cgroup_rstat_lock);
 147
 148         for_each_possible_cpu(cpu) {
 149                 raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock,
 150                                                        cpu);
 151                 struct cgroup *pos = NULL;
 152
 153                 raw_spin_lock(cpu_lock);
 154                 while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) {
 155                         struct cgroup_subsys_state *css;
 156
 157                         cgroup_base_stat_flush(pos, cpu);
 158
 159                         rcu_read_lock();
 160                         list_for_each_entry_rcu(css, &pos->rstat_css_list,
 161                                                 rstat_css_node)
 162                                 css->ss->css_rstat_flush(css, cpu);
 163                         rcu_read_unlock();
 164                 }
 165                 raw_spin_unlock(cpu_lock);
 166
 167                 /* if @may_sleep, play nice and yield if necessary */
 168                 if (may_sleep && (need_resched() ||
 169                                   spin_needbreak(&cgroup_rstat_lock))) {
 170                         spin_unlock_irq(&cgroup_rstat_lock);
 171                         if (!cond_resched())
 172                                 cpu_relax();
 173                         spin_lock_irq(&cgroup_rstat_lock);
 174                 }
 175         }
 176 }
 177
 178 /**
 179  * cgroup_rstat_flush - flush stats in @cgrp's subtree
 180  * @cgrp: target cgroup
 181  *
 182  * Collect all per-cpu stats in @cgrp's subtree into the global counters
 183  * and propagate them upwards.  After this function returns, all cgroups in
 184  * the subtree have up-to-date ->stat.
 185  *
 186  * This also gets all cgroups in the subtree including @cgrp off the
 187  * ->updated_children lists.
 188  *
 189  * This function may block.
 190  */
 191 void cgroup_rstat_flush(struct cgroup *cgrp)
 192 {
 193         might_sleep();
 194
 195         spin_lock_irq(&cgroup_rstat_lock);
 196         cgroup_rstat_flush_locked(cgrp, true);
 197         spin_unlock_irq(&cgroup_rstat_lock);
 198 }
 199
 200 /**
 201  * cgroup_rstat_flush_irqsafe - irqsafe version of cgroup_rstat_flush()
 202  * @cgrp: target cgroup
 203  *
 204  * This function can be called from any context.
 205  */
 206 void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp)
 207 {
 208         unsigned long flags;
 209
 210         spin_lock_irqsave(&cgroup_rstat_lock, flags);
 211         cgroup_rstat_flush_locked(cgrp, false);
 212         spin_unlock_irqrestore(&cgroup_rstat_lock, flags);
 213 }
 214
 215 /**
 216  * cgroup_rstat_flush_begin - flush stats in @cgrp's subtree and hold
 217  * @cgrp: target cgroup
 218  *
 219  * Flush stats in @cgrp's subtree and prevent further flushes.  Must be
 220  * paired with cgroup_rstat_flush_release().
 221  *
 222  * This function may block.
 223  */
 224 void cgroup_rstat_flush_hold(struct cgroup *cgrp)
 225         __acquires(&cgroup_rstat_lock)
 226 {
 227         might_sleep();
 228         spin_lock_irq(&cgroup_rstat_lock);
 229         cgroup_rstat_flush_locked(cgrp, true);
 230 }
 231
 232 /**
 233  * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
 234  */
 235 void cgroup_rstat_flush_release(void)
 236         __releases(&cgroup_rstat_lock)
 237 {
 238         spin_unlock_irq(&cgroup_rstat_lock);
 239 }
 240
 241 int cgroup_rstat_init(struct cgroup *cgrp)
 242 {
 243         int cpu;
 244
 245         /* the root cgrp has rstat_cpu preallocated */
 246         if (!cgrp->rstat_cpu) {
 247                 cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
 248                 if (!cgrp->rstat_cpu)
 249                         return -ENOMEM;
 250         }
 251
 252         /* ->updated_children list is self terminated */
 253         for_each_possible_cpu(cpu) {
 254                 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
 255
 256                 rstatc->updated_children = cgrp;
 257                 u64_stats_init(&rstatc->bsync);
 258         }
 259
 260         return 0;
 261 }
 262
 263 void cgroup_rstat_exit(struct cgroup *cgrp)
 264 {
 265         int cpu;
 266
 267         cgroup_rstat_flush(cgrp);
 268
 269         /* sanity check */
 270         for_each_possible_cpu(cpu) {
 271                 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
 272
 273                 if (WARN_ON_ONCE(rstatc->updated_children != cgrp) ||
 274                     WARN_ON_ONCE(rstatc->updated_next))
 275                         return;
 276         }
 277
 278         free_percpu(cgrp->rstat_cpu);
 279         cgrp->rstat_cpu = NULL;
 280 }
 281
 282 void __init cgroup_rstat_boot(void)
 283 {
 284         int cpu;
 285
 286         for_each_possible_cpu(cpu)
 287                 raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
 288
 289         BUG_ON(cgroup_rstat_init(&cgrp_dfl_root.cgrp));
 290 }
 291
 292 /*
 293  * Functions for cgroup basic resource statistics implemented on top of
 294  * rstat.
 295  */
 296 static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
 297                                  struct cgroup_base_stat *src_bstat)
 298 {
 299         dst_bstat->cputime.utime += src_bstat->cputime.utime;
 300         dst_bstat->cputime.stime += src_bstat->cputime.stime;
 301         dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
 302 }
 303
 304 static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
 305                                  struct cgroup_base_stat *src_bstat)
 306 {
 307         dst_bstat->cputime.utime -= src_bstat->cputime.utime;
 308         dst_bstat->cputime.stime -= src_bstat->cputime.stime;
 309         dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
 310 }
 311
 312 static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 313 {
 314         struct cgroup *parent = cgroup_parent(cgrp);
 315         struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
 316         struct cgroup_base_stat cur, delta;
 317         unsigned seq;
 318
 319         /* fetch the current per-cpu values */
 320         do {
 321                 seq = __u64_stats_fetch_begin(&rstatc->bsync);
 322                 cur.cputime = rstatc->bstat.cputime;
 323         } while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
 324
 325         /* propagate percpu delta to global */
 326         delta = cur;
 327         cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
 328         cgroup_base_stat_add(&cgrp->bstat, &delta);
 329         cgroup_base_stat_add(&rstatc->last_bstat, &delta);
 330
 331         /* propagate global delta to parent */
 332         if (parent) {
 333                 delta = cgrp->bstat;
 334                 cgroup_base_stat_sub(&delta, &cgrp->last_bstat);
 335                 cgroup_base_stat_add(&parent->bstat, &delta);
 336                 cgroup_base_stat_add(&cgrp->last_bstat, &delta);
 337         }
 338 }
 339
 340 static struct cgroup_rstat_cpu *
 341 cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp)
 342 {
 343         struct cgroup_rstat_cpu *rstatc;
 344
 345         rstatc = get_cpu_ptr(cgrp->rstat_cpu);
 346         u64_stats_update_begin(&rstatc->bsync);
 347         return rstatc;
 348 }
 349
 350 static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
 351                                                  struct cgroup_rstat_cpu *rstatc)
 352 {
 353         u64_stats_update_end(&rstatc->bsync);
 354         cgroup_rstat_updated(cgrp, smp_processor_id());
 355         put_cpu_ptr(rstatc);
 356 }
 357
 358 void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
 359 {
 360         struct cgroup_rstat_cpu *rstatc;
 361
 362         rstatc = cgroup_base_stat_cputime_account_begin(cgrp);
 363         rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
 364         cgroup_base_stat_cputime_account_end(cgrp, rstatc);
 365 }
 366
 367 void __cgroup_account_cputime_field(struct cgroup *cgrp,
 368                                     enum cpu_usage_stat index, u64 delta_exec)
 369 {
 370         struct cgroup_rstat_cpu *rstatc;
 371
 372         rstatc = cgroup_base_stat_cputime_account_begin(cgrp);
 373
 374         switch (index) {
 375         case CPUTIME_USER:
 376         case CPUTIME_NICE:
 377                 rstatc->bstat.cputime.utime += delta_exec;
 378                 break;
 379         case CPUTIME_SYSTEM:
 380         case CPUTIME_IRQ:
 381         case CPUTIME_SOFTIRQ:
 382                 rstatc->bstat.cputime.stime += delta_exec;
 383                 break;
 384         default:
 385                 break;
 386         }
 387
 388         cgroup_base_stat_cputime_account_end(cgrp, rstatc);
 389 }
 390
 391 /*
 392  * compute the cputime for the root cgroup by getting the per cpu data
 393  * at a global level, then categorizing the fields in a manner consistent
 394  * with how it is done by __cgroup_account_cputime_field for each bit of
 395  * cpu time attributed to a cgroup.
 396  */
 397 static void root_cgroup_cputime(struct task_cputime *cputime)
 398 {
 399         int i;
 400
 401         cputime->stime = 0;
 402         cputime->utime = 0;
 403         cputime->sum_exec_runtime = 0;
 404         for_each_possible_cpu(i) {
 405                 struct kernel_cpustat kcpustat;
 406                 u64 *cpustat = kcpustat.cpustat;
 407                 u64 user = 0;
 408                 u64 sys = 0;
 409
 410                 kcpustat_cpu_fetch(&kcpustat, i);
 411
 412                 user += cpustat[CPUTIME_USER];
 413                 user += cpustat[CPUTIME_NICE];
 414                 cputime->utime += user;
 415
 416                 sys += cpustat[CPUTIME_SYSTEM];
 417                 sys += cpustat[CPUTIME_IRQ];
 418                 sys += cpustat[CPUTIME_SOFTIRQ];
 419                 cputime->stime += sys;
 420
 421                 cputime->sum_exec_runtime += user;
 422                 cputime->sum_exec_runtime += sys;
 423                 cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
 424                 cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST];
 425                 cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST_NICE];
 426         }
 427 }
 428
 429 void cgroup_base_stat_cputime_show(struct seq_file *seq)
 430 {
 431         struct cgroup *cgrp = seq_css(seq)->cgroup;
 432         u64 usage, utime, stime;
 433         struct task_cputime cputime;
 434
 435         if (cgroup_parent(cgrp)) {
 436                 cgroup_rstat_flush_hold(cgrp);
 437                 usage = cgrp->bstat.cputime.sum_exec_runtime;
 438                 cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
 439                                &utime, &stime);
 440                 cgroup_rstat_flush_release();
 441         } else {
 442                 root_cgroup_cputime(&cputime);
 443                 usage = cputime.sum_exec_runtime;
 444                 utime = cputime.utime;
 445                 stime = cputime.stime;
 446         }
 447
 448         do_div(usage, NSEC_PER_USEC);
 449         do_div(utime, NSEC_PER_USEC);
 450         do_div(stime, NSEC_PER_USEC);
 451
 452         seq_printf(seq, "usage_usec %llu\n"
 453                    "user_usec %llu\n"
 454                    "system_usec %llu\n",
 455                    usage, utime, stime);
 456 }