diff options
Diffstat (limited to 'kernel/cpuset.c')
| -rw-r--r-- | kernel/cpuset.c | 275 |
1 files changed, 270 insertions, 5 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 1133062395e..203ca52e78d 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -4,7 +4,7 @@ * Processor and Memory placement constraints for sets of tasks. * * Copyright (C) 2003 BULL SA. - * Copyright (C) 2004-2006 Silicon Graphics, Inc. + * Copyright (C) 2004-2007 Silicon Graphics, Inc. * Copyright (C) 2006 Google, Inc * * Portions derived from Patrick Mochel's sysfs code. @@ -54,6 +54,7 @@ #include <asm/uaccess.h> #include <asm/atomic.h> #include <linux/mutex.h> +#include <linux/kfifo.h> /* * Tracks how many cpusets are currently defined in system. @@ -91,6 +92,9 @@ struct cpuset { int mems_generation; struct fmeter fmeter; /* memory_pressure filter */ + + /* partition number for rebuild_sched_domains() */ + int pn; }; /* Retrieve the cpuset for a cgroup */ @@ -113,6 +117,7 @@ typedef enum { CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE, CS_MEMORY_MIGRATE, + CS_SCHED_LOAD_BALANCE, CS_SPREAD_PAGE, CS_SPREAD_SLAB, } cpuset_flagbits_t; @@ -128,6 +133,11 @@ static inline int is_mem_exclusive(const struct cpuset *cs) return test_bit(CS_MEM_EXCLUSIVE, &cs->flags); } +static inline int is_sched_load_balance(const struct cpuset *cs) +{ + return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags); +} + static inline int is_memory_migrate(const struct cpuset *cs) { return test_bit(CS_MEMORY_MIGRATE, &cs->flags); @@ -482,6 +492,208 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial) } /* + * Helper routine for rebuild_sched_domains(). + * Do cpusets a, b have overlapping cpus_allowed masks? + */ + +static int cpusets_overlap(struct cpuset *a, struct cpuset *b) +{ + return cpus_intersects(a->cpus_allowed, b->cpus_allowed); +} + +/* + * rebuild_sched_domains() + * + * If the flag 'sched_load_balance' of any cpuset with non-empty + * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset + * which has that flag enabled, or if any cpuset with a non-empty + * 'cpus' is removed, then call this routine to rebuild the + * scheduler's dynamic sched domains. + * + * This routine builds a partial partition of the systems CPUs + * (the set of non-overlappping cpumask_t's in the array 'part' + * below), and passes that partial partition to the kernel/sched.c + * partition_sched_domains() routine, which will rebuild the + * schedulers load balancing domains (sched domains) as specified + * by that partial partition. A 'partial partition' is a set of + * non-overlapping subsets whose union is a subset of that set. + * + * See "What is sched_load_balance" in Documentation/cpusets.txt + * for a background explanation of this. + * + * Does not return errors, on the theory that the callers of this + * routine would rather not worry about failures to rebuild sched + * domains when operating in the severe memory shortage situations + * that could cause allocation failures below. + * + * Call with cgroup_mutex held. May take callback_mutex during + * call due to the kfifo_alloc() and kmalloc() calls. May nest + * a call to the lock_cpu_hotplug()/unlock_cpu_hotplug() pair. + * Must not be called holding callback_mutex, because we must not + * call lock_cpu_hotplug() while holding callback_mutex. Elsewhere + * the kernel nests callback_mutex inside lock_cpu_hotplug() calls. + * So the reverse nesting would risk an ABBA deadlock. + * + * The three key local variables below are: + * q - a kfifo queue of cpuset pointers, used to implement a + * top-down scan of all cpusets. This scan loads a pointer + * to each cpuset marked is_sched_load_balance into the + * array 'csa'. For our purposes, rebuilding the schedulers + * sched domains, we can ignore !is_sched_load_balance cpusets. + * csa - (for CpuSet Array) Array of pointers to all the cpusets + * that need to be load balanced, for convenient iterative + * access by the subsequent code that finds the best partition, + * i.e the set of domains (subsets) of CPUs such that the + * cpus_allowed of every cpuset marked is_sched_load_balance + * is a subset of one of these domains, while there are as + * many such domains as possible, each as small as possible. + * doms - Conversion of 'csa' to an array of cpumasks, for passing to + * the kernel/sched.c routine partition_sched_domains() in a + * convenient format, that can be easily compared to the prior + * value to determine what partition elements (sched domains) + * were changed (added or removed.) + * + * Finding the best partition (set of domains): + * The triple nested loops below over i, j, k scan over the + * load balanced cpusets (using the array of cpuset pointers in + * csa[]) looking for pairs of cpusets that have overlapping + * cpus_allowed, but which don't have the same 'pn' partition + * number and gives them in the same partition number. It keeps + * looping on the 'restart' label until it can no longer find + * any such pairs. + * + * The union of the cpus_allowed masks from the set of + * all cpusets having the same 'pn' value then form the one + * element of the partition (one sched domain) to be passed to + * partition_sched_domains(). + */ + +static void rebuild_sched_domains(void) +{ + struct kfifo *q; /* queue of cpusets to be scanned */ + struct cpuset *cp; /* scans q */ + struct cpuset **csa; /* array of all cpuset ptrs */ + int csn; /* how many cpuset ptrs in csa so far */ + int i, j, k; /* indices for partition finding loops */ + cpumask_t *doms; /* resulting partition; i.e. sched domains */ + int ndoms; /* number of sched domains in result */ + int nslot; /* next empty doms[] cpumask_t slot */ + + q = NULL; + csa = NULL; + doms = NULL; + + /* Special case for the 99% of systems with one, full, sched domain */ + if (is_sched_load_balance(&top_cpuset)) { + ndoms = 1; + doms = kmalloc(sizeof(cpumask_t), GFP_KERNEL); + if (!doms) + goto rebuild; + *doms = top_cpuset.cpus_allowed; + goto rebuild; + } + + q = kfifo_alloc(number_of_cpusets * sizeof(cp), GFP_KERNEL, NULL); + if (IS_ERR(q)) + goto done; + csa = kmalloc(number_of_cpusets * sizeof(cp), GFP_KERNEL); + if (!csa) + goto done; + csn = 0; + + cp = &top_cpuset; + __kfifo_put(q, (void *)&cp, sizeof(cp)); + while (__kfifo_get(q, (void *)&cp, sizeof(cp))) { + struct cgroup *cont; + struct cpuset *child; /* scans child cpusets of cp */ + if (is_sched_load_balance(cp)) + csa[csn++] = cp; + list_for_each_entry(cont, &cp->css.cgroup->children, sibling) { + child = cgroup_cs(cont); + __kfifo_put(q, (void *)&child, sizeof(cp)); + } + } + + for (i = 0; i < csn; i++) + csa[i]->pn = i; + ndoms = csn; + +restart: + /* Find the best partition (set of sched domains) */ + for (i = 0; i < csn; i++) { + struct cpuset *a = csa[i]; + int apn = a->pn; + + for (j = 0; j < csn; j++) { + struct cpuset *b = csa[j]; + int bpn = b->pn; + + if (apn != bpn && cpusets_overlap(a, b)) { + for (k = 0; k < csn; k++) { + struct cpuset *c = csa[k]; + + if (c->pn == bpn) + c->pn = apn; + } + ndoms--; /* one less element */ + goto restart; + } + } + } + + /* Convert <csn, csa> to <ndoms, doms> */ + doms = kmalloc(ndoms * sizeof(cpumask_t), GFP_KERNEL); + if (!doms) + goto rebuild; + + for (nslot = 0, i = 0; i < csn; i++) { + struct cpuset *a = csa[i]; + int apn = a->pn; + + if (apn >= 0) { + cpumask_t *dp = doms + nslot; + + if (nslot == ndoms) { + static int warnings = 10; + if (warnings) { + printk(KERN_WARNING + "rebuild_sched_domains confused:" + " nslot %d, ndoms %d, csn %d, i %d," + " apn %d\n", + nslot, ndoms, csn, i, apn); + warnings--; + } + continue; + } + + cpus_clear(*dp); + for (j = i; j < csn; j++) { + struct cpuset *b = csa[j]; + + if (apn == b->pn) { + cpus_or(*dp, *dp, b->cpus_allowed); + b->pn = -1; + } + } + nslot++; + } + } + BUG_ON(nslot != ndoms); + +rebuild: + /* Have scheduler rebuild sched domains */ + lock_cpu_hotplug(); + partition_sched_domains(ndoms, doms); + unlock_cpu_hotplug(); + +done: + if (q && !IS_ERR(q)) + kfifo_free(q); + kfree(csa); + /* Don't kfree(doms) -- partition_sched_domains() does that. */ +} + +/* * Call with manage_mutex held. May take callback_mutex during call. */ @@ -489,6 +701,7 @@ static int update_cpumask(struct cpuset *cs, char *buf) { struct cpuset trialcs; int retval; + int cpus_changed, is_load_balanced; /* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */ if (cs == &top_cpuset) @@ -516,9 +729,17 @@ static int update_cpumask(struct cpuset *cs, char *buf) retval = validate_change(cs, &trialcs); if (retval < 0) return retval; + + cpus_changed = !cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed); + is_load_balanced = is_sched_load_balance(&trialcs); + mutex_lock(&callback_mutex); cs->cpus_allowed = trialcs.cpus_allowed; mutex_unlock(&callback_mutex); + + if (cpus_changed && is_load_balanced) + rebuild_sched_domains(); + return 0; } @@ -752,6 +973,7 @@ static int update_memory_pressure_enabled(struct cpuset *cs, char *buf) /* * update_flag - read a 0 or a 1 in a file and update associated flag * bit: the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE, + * CS_SCHED_LOAD_BALANCE, * CS_NOTIFY_ON_RELEASE, CS_MEMORY_MIGRATE, * CS_SPREAD_PAGE, CS_SPREAD_SLAB) * cs: the cpuset to update @@ -765,6 +987,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf) int turning_on; struct cpuset trialcs; int err; + int cpus_nonempty, balance_flag_changed; turning_on = (simple_strtoul(buf, NULL, 10) != 0); @@ -777,10 +1000,18 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf) err = validate_change(cs, &trialcs); if (err < 0) return err; + + cpus_nonempty = !cpus_empty(trialcs.cpus_allowed); + balance_flag_changed = (is_sched_load_balance(cs) != + is_sched_load_balance(&trialcs)); + mutex_lock(&callback_mutex); cs->flags = trialcs.flags; mutex_unlock(&callback_mutex); + if (cpus_nonempty && balance_flag_changed) + rebuild_sched_domains(); + return 0; } @@ -928,6 +1159,7 @@ typedef enum { FILE_MEMLIST, FILE_CPU_EXCLUSIVE, FILE_MEM_EXCLUSIVE, + FILE_SCHED_LOAD_BALANCE, FILE_MEMORY_PRESSURE_ENABLED, FILE_MEMORY_PRESSURE, FILE_SPREAD_PAGE, @@ -946,7 +1178,7 @@ static ssize_t cpuset_common_file_write(struct cgroup *cont, int retval = 0; /* Crude upper limit on largest legitimate cpulist user might write. */ - if (nbytes > 100 + 6 * max(NR_CPUS, MAX_NUMNODES)) + if (nbytes > 100U + 6 * max(NR_CPUS, MAX_NUMNODES)) return -E2BIG; /* +1 for nul-terminator */ @@ -979,6 +1211,9 @@ static ssize_t cpuset_common_file_write(struct cgroup *cont, case FILE_MEM_EXCLUSIVE: retval = update_flag(CS_MEM_EXCLUSIVE, cs, buffer); break; + case FILE_SCHED_LOAD_BALANCE: + retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, buffer); + break; case FILE_MEMORY_MIGRATE: retval = update_flag(CS_MEMORY_MIGRATE, cs, buffer); break; @@ -1074,6 +1309,9 @@ static ssize_t cpuset_common_file_read(struct cgroup *cont, case FILE_MEM_EXCLUSIVE: *s++ = is_mem_exclusive(cs) ? '1' : '0'; break; + case FILE_SCHED_LOAD_BALANCE: + *s++ = is_sched_load_balance(cs) ? '1' : '0'; + break; case FILE_MEMORY_MIGRATE: *s++ = is_memory_migrate(cs) ? '1' : '0'; break; @@ -1137,6 +1375,13 @@ static struct cftype cft_mem_exclusive = { .private = FILE_MEM_EXCLUSIVE, }; +static struct cftype cft_sched_load_balance = { + .name = "sched_load_balance", + .read = cpuset_common_file_read, + .write = cpuset_common_file_write, + .private = FILE_SCHED_LOAD_BALANCE, +}; + static struct cftype cft_memory_migrate = { .name = "memory_migrate", .read = cpuset_common_file_read, @@ -1186,6 +1431,8 @@ static int cpuset_populate(struct cgroup_subsys *ss, struct cgroup *cont) return err; if ((err = cgroup_add_file(cont, ss, &cft_memory_migrate)) < 0) return err; + if ((err = cgroup_add_file(cont, ss, &cft_sched_load_balance)) < 0) + return err; if ((err = cgroup_add_file(cont, ss, &cft_memory_pressure)) < 0) return err; if ((err = cgroup_add_file(cont, ss, &cft_spread_page)) < 0) @@ -1267,6 +1514,7 @@ static struct cgroup_subsys_state *cpuset_create( set_bit(CS_SPREAD_PAGE, &cs->flags); if (is_spread_slab(parent)) set_bit(CS_SPREAD_SLAB, &cs->flags); + set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags); cs->cpus_allowed = CPU_MASK_NONE; cs->mems_allowed = NODE_MASK_NONE; cs->mems_generation = cpuset_mems_generation++; @@ -1277,11 +1525,27 @@ static struct cgroup_subsys_state *cpuset_create( return &cs->css ; } +/* + * Locking note on the strange update_flag() call below: + * + * If the cpuset being removed has its flag 'sched_load_balance' + * enabled, then simulate turning sched_load_balance off, which + * will call rebuild_sched_domains(). The lock_cpu_hotplug() + * call in rebuild_sched_domains() must not be made while holding + * callback_mutex. Elsewhere the kernel nests callback_mutex inside + * lock_cpu_hotplug() calls. So the reverse nesting would risk an + * ABBA deadlock. + */ + static void cpuset_destroy(struct cgroup_subsys *ss, struct cgroup *cont) { struct cpuset *cs = cgroup_cs(cont); cpuset_update_task_memory_state(); + + if (is_sched_load_balance(cs)) + update_flag(CS_SCHED_LOAD_BALANCE, cs, "0"); + number_of_cpusets--; kfree(cs); } @@ -1326,6 +1590,7 @@ int __init cpuset_init(void) fmeter_init(&top_cpuset.fmeter); top_cpuset.mems_generation = cpuset_mems_generation++; + set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags); err = register_filesystem(&cpuset_fs_type); if (err < 0) @@ -1412,8 +1677,8 @@ static void common_cpu_mem_hotplug_unplug(void) * cpu_online_map on each CPU hotplug (cpuhp) event. */ -static int cpuset_handle_cpuhp(struct notifier_block *nb, - unsigned long phase, void *cpu) +static int cpuset_handle_cpuhp(struct notifier_block *unused_nb, + unsigned long phase, void *unused_cpu) { if (phase == CPU_DYING || phase == CPU_DYING_FROZEN) return NOTIFY_DONE; @@ -1803,7 +2068,7 @@ void __cpuset_memory_pressure_bump(void) * the_top_cpuset_hack in cpuset_exit(), which sets an exiting tasks * cpuset to top_cpuset. */ -static int proc_cpuset_show(struct seq_file *m, void *v) +static int proc_cpuset_show(struct seq_file *m, void *unused_v) { struct pid *pid; struct task_struct *tsk; |