From 02caa430beb36ff10deb1f5347eb4ae71e86084c Mon Sep 17 00:00:00 2001 From: San Mehat Date: Wed, 5 May 2010 11:38:42 -0700 Subject: staging: android: lowmemkiller: Substantially reduce overhead during reclaim This patch optimizes lowmemkiller to not do any work when it has an outstanding kill-request. This greatly reduces the pressure on the task_list lock (improving interactivity), as well as improving the vmscan performance when under heavy memory pressure (by up to 20x in tests). Note: For this enhancement to work, you need CONFIG_PROFILING Signed-off-by: San Mehat --- drivers/staging/android/lowmemorykiller.c | 43 +++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'drivers/staging') diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c index 83721786dead..4523093767d4 100644 --- a/drivers/staging/android/lowmemorykiller.c +++ b/drivers/staging/android/lowmemorykiller.c @@ -34,6 +34,8 @@ #include #include #include +#include +#include static uint32_t lowmem_debug_level = 2; static int lowmem_adj[6] = { @@ -51,12 +53,32 @@ static size_t lowmem_minfree[6] = { }; static int lowmem_minfree_size = 4; +static struct task_struct *lowmem_deathpending; + #define lowmem_print(level, x...) \ do { \ if (lowmem_debug_level >= (level)) \ printk(x); \ } while (0) +static int +task_notify_func(struct notifier_block *self, unsigned long val, void *data); + +static struct notifier_block task_nb = { + .notifier_call = task_notify_func, +}; + +static int +task_notify_func(struct notifier_block *self, unsigned long val, void *data) +{ + struct task_struct *task = data; + if (task == lowmem_deathpending) { + lowmem_deathpending = NULL; + task_handoff_unregister(&task_nb); + } + return NOTIFY_OK; +} + static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask) { struct task_struct *p; @@ -71,6 +93,18 @@ static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask) int other_free = global_page_state(NR_FREE_PAGES); int other_file = global_page_state(NR_FILE_PAGES); + /* + * If we already have a death outstanding, then + * bail out right away; indicating to vmscan + * that we have nothing further to offer on + * this pass. + * + * Note: Currently you need CONFIG_PROFILING + * for this to work correctly. + */ + if (lowmem_deathpending) + return 0; + if (lowmem_adj_size < array_size) array_size = lowmem_adj_size; if (lowmem_minfree_size < array_size) @@ -142,6 +176,15 @@ static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask) lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n", selected->pid, selected->comm, selected_oom_adj, selected_tasksize); + /* + * If CONFIG_PROFILING is off, then task_handoff_register() + * is a nop. In that case we don't want to stall the killer + * by setting lowmem_deathpending. + */ +#ifdef CONFIG_PROFILING + lowmem_deathpending = selected; + task_handoff_register(&task_nb); +#endif force_sig(SIGKILL, selected); rem -= selected_tasksize; } -- cgit v1.2.3