diff options
| -rw-r--r-- | mm/Kconfig | 13 | ||||
| -rw-r--r-- | mm/vmscan.c | 30 |
2 files changed, 41 insertions, 2 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index 3ca6a255de03..7b7eae150c4e 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -628,6 +628,19 @@ config BALANCE_ANON_FILE_RECLAIM Swapping anonymous pages out to memory can be efficient enough to justify treating anonymous and file backed pages equally. +config KSWAPD_CPU_AFFINITY_MASK + string "kswapd cpu affinity mask" + depends on SMP + help + Set the cpu affinity for the kswapd task. + There can be power benefits on certain targets when limiting kswapd + to run only on certain cores. + The cpu affinity bitmask is represented by a hex string where commas + group hex digits into chunks. Each chunk defines exactly 32 bits of + the resultant bitmask. + For example to limit kswapd to the first 4 cores use the following: + CONFIG_KSWAPD_CPU_AFFINITY_MASK="f" + # For architectures that support deferred memory initialisation config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT bool diff --git a/mm/vmscan.c b/mm/vmscan.c index 31713a87fa7b..194c534da9ba 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -147,6 +147,12 @@ int vm_swappiness = 60; */ unsigned long vm_total_pages; +#ifdef CONFIG_KSWAPD_CPU_AFFINITY_MASK +char *kswapd_cpu_mask = CONFIG_KSWAPD_CPU_AFFINITY_MASK; +#else +char *kswapd_cpu_mask = NULL; +#endif + static LIST_HEAD(shrinker_list); static DECLARE_RWSEM(shrinker_rwsem); @@ -3485,7 +3491,7 @@ static int kswapd(void *p) lockdep_set_current_reclaim_state(GFP_KERNEL); - if (!cpumask_empty(cpumask)) + if (kswapd_cpu_mask == NULL && !cpumask_empty(cpumask)) set_cpus_allowed_ptr(tsk, cpumask); current->reclaim_state = &reclaim_state; @@ -3655,6 +3661,22 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action, return NOTIFY_OK; } +static int set_kswapd_cpu_mask(pg_data_t *pgdat) +{ + int ret = 0; + cpumask_t tmask; + + if (!kswapd_cpu_mask) + return 0; + + cpumask_clear(&tmask); + ret = cpumask_parse(kswapd_cpu_mask, &tmask); + if (ret) + return ret; + + return set_cpus_allowed_ptr(pgdat->kswapd, &tmask); +} + /* * This kswapd start function will be called by init and node-hot-add. * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. @@ -3674,6 +3696,9 @@ int kswapd_run(int nid) pr_err("Failed to start kswapd on node %d\n", nid); ret = PTR_ERR(pgdat->kswapd); pgdat->kswapd = NULL; + } else if (kswapd_cpu_mask) { + if (set_kswapd_cpu_mask(pgdat)) + pr_warn("error setting kswapd cpu affinity mask\n"); } return ret; } @@ -3699,7 +3724,8 @@ static int __init kswapd_init(void) swap_setup(); for_each_node_state(nid, N_MEMORY) kswapd_run(nid); - hotcpu_notifier(cpu_callback, 0); + if (kswapd_cpu_mask == NULL) + hotcpu_notifier(cpu_callback, 0); return 0; } |