projects / ipfire-2.x.git / blame
| Commit | Line | Data |
|---|---|---|
| 2cb7cef9 BS |
1 | Subject: add affinity_load_balancing sysctl |
| 2 | From: kraxel@suse.de | |
| 3 | References: 176738 | |
| 4 | ||
| 5 | Add a sysctl to tweak how the kernel initially schedules threads to cpus. | |
| 6 | ||
| 7 | By default the kernel tries to keep threads on the local cpu (and local | |
| 8 | node on NUMA machines). Depending on the application this may not deliver | |
| 9 | the best performance, especially applications with a large working set for | |
| 10 | each thread tend to perform better when being scheduled to different nodes | |
| 11 | because they can use caches of multiple nodes then. | |
| 12 | ||
| 13 | With this sysctl enabled the kernel will spread threads over the cpus given | |
| 14 | and doesn't try to keep them local. | |
| 15 | ||
| 16 | usage: | |
| 17 | - set sysctl kernel.affinity_load_balancing = 1 | |
| 18 | - use taskset or numactl to specify which cpus your task should be | |
| 19 | scheduled on. | |
| 20 | ||
| 21 | --- | |
| 22 | kernel/sched.c | 28 ++++++++++++++++++++++++++++ | |
| 23 | kernel/sysctl.c | 12 ++++++++++++ | |
| 24 | 2 files changed, 40 insertions(+) | |
| 25 | ||
| 26 | --- a/kernel/sched.c | |
| 27 | +++ b/kernel/sched.c | |
| 28 | @@ -2107,6 +2107,28 @@ find_idlest_cpu(struct sched_group *grou | |
| 29 | return idlest; | |
| 30 | } | |
| 31 | ||
| 32 | +static int | |
| 33 | +find_idlest_cpu_nodomain(struct task_struct *p, int this_cpu) | |
| 34 | +{ | |
| 35 | + cpumask_t tmp; | |
| 36 | + unsigned long load, min_load = ULONG_MAX; | |
| 37 | + int idlest = -1; | |
| 38 | + int i; | |
| 39 | + | |
| 40 | + /* Traverse only the allowed CPUs */ | |
| 41 | + cpus_and(tmp, cpu_online_map, p->cpus_allowed); | |
| 42 | + | |
| 43 | + for_each_cpu_mask(i, tmp) { | |
| 44 | + load = target_load(i, 1); | |
| 45 | + | |
| 46 | + if (load < min_load) { | |
| 47 | + min_load = load; | |
| 48 | + idlest = i; | |
| 49 | + } | |
| 50 | + } | |
| 51 | + return idlest; | |
| 52 | +} | |
| 53 | + | |
| 54 | /* | |
| 55 | * sched_balance_self: balance the current task (running on cpu) in domains | |
| 56 | * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and | |
| 57 | @@ -2118,11 +2140,17 @@ find_idlest_cpu(struct sched_group *grou | |
| 58 | * | |
| 59 | * preempt must be disabled. | |
| 60 | */ | |
| 61 | + | |
| 62 | +int affinity_load_balancing = 0; | |
| 63 | + | |
| 64 | static int sched_balance_self(int cpu, int flag) | |
| 65 | { | |
| 66 | struct task_struct *t = current; | |
| 67 | struct sched_domain *tmp, *sd = NULL; | |
| 68 | ||
| 69 | + if (affinity_load_balancing && !cpus_full(t->cpus_allowed)) | |
| 70 | + return find_idlest_cpu_nodomain(t, cpu); | |
| 71 | + | |
| 72 | for_each_domain(cpu, tmp) { | |
| 73 | /* | |
| 74 | * If power savings logic is enabled for a domain, stop there. | |
| 75 | --- a/kernel/sysctl.c | |
| 76 | +++ b/kernel/sysctl.c | |
| 77 | @@ -237,6 +237,8 @@ static int min_wakeup_granularity_ns; | |
| 78 | static int max_wakeup_granularity_ns = NSEC_PER_SEC; /* 1 second */ | |
| 79 | #endif | |
| 80 | ||
| 81 | +extern int affinity_load_balancing; | |
| 82 | + | |
| 83 | static struct ctl_table kern_table[] = { | |
| 84 | #ifdef CONFIG_SCHED_DEBUG | |
| 85 | { | |
| 86 | @@ -872,6 +874,16 @@ static struct ctl_table kern_table[] = { | |
| 87 | * NOTE: do not add new entries to this table unless you have read | |
| 88 | * Documentation/sysctl/ctl_unnumbered.txt | |
| 89 | */ | |
| 90 | +#ifdef CONFIG_SMP | |
| 91 | + { | |
| 92 | + .ctl_name = CTL_UNNUMBERED, | |
| 93 | + .procname = "affinity_load_balancing", | |
| 94 | + .data = &affinity_load_balancing, | |
| 95 | + .maxlen = sizeof(affinity_load_balancing), | |
| 96 | + .mode = 0644, | |
| 97 | + .proc_handler = &proc_dointvec, | |
| 98 | + }, | |
| 99 | +#endif | |
| 100 | { .ctl_name = 0 } | |
| 101 | }; | |
| 102 |