From: Huang Ying <[email protected]> The statistics for total readahead pages and total readahead hits are recorded and exported via the following sysfs interface.
/sys/kernel/mm/swap/ra_hits /sys/kernel/mm/swap/ra_total With them, the efficiency of the swap readahead could be measured, so that the swap readahead algorithm and parameters could be tuned accordingly. Signed-off-by: "Huang, Ying" <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Fengguang Wu <[email protected]> Cc: Tim Chen <[email protected]> Cc: Dave Hansen <[email protected]> --- mm/swap_state.c | 38 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 36 insertions(+), 2 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index a13bbf504e93..8be7153967ed 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -20,6 +20,7 @@ #include <linux/vmalloc.h> #include <linux/swap_slots.h> #include <linux/huge_mm.h> +#include <linux/percpu_counter.h> #include <asm/pgtable.h> @@ -74,6 +75,15 @@ unsigned long total_swapcache_pages(void) } static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); +static struct percpu_counter swapin_readahead_hits_total; +static struct percpu_counter swapin_readahead_total; + +static int __init swap_init(void) +{ + percpu_counter_init(&swapin_readahead_hits_total, 0, GFP_KERNEL); + percpu_counter_init(&swapin_readahead_total, 0, GFP_KERNEL); +} +subsys_initcall(swap_init); void show_swap_cache_info(void) { @@ -305,8 +315,10 @@ struct page * lookup_swap_cache(swp_entry_t entry) if (page && likely(!PageTransCompound(page))) { INC_CACHE_INFO(find_success); - if (TestClearPageReadahead(page)) + if (TestClearPageReadahead(page)) { atomic_inc(&swapin_readahead_hits); + percpu_counter_inc(&swapin_readahead_hits_total); + } } INC_CACHE_INFO(find_total); @@ -516,8 +528,11 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, gfp_mask, vma, addr, false); if (!page) continue; - if (offset != entry_offset && likely(!PageTransCompound(page))) + if (offset != entry_offset && + likely(!PageTransCompound(page))) { SetPageReadahead(page); + percpu_counter_inc(&swapin_readahead_total); + } put_page(page); } blk_finish_plug(&plug); @@ -603,12 +618,31 @@ static ssize_t swap_cache_find_total_show( static struct kobj_attribute swap_cache_find_total_attr = __ATTR(cache_find_total, 0444, swap_cache_find_total_show, NULL); +static ssize_t swap_readahead_hits_show( + struct kobject *kobj, struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lld\n", + percpu_counter_sum(&swapin_readahead_hits_total)); +} +static struct kobj_attribute swap_readahead_hits_attr = + __ATTR(ra_hits, 0444, swap_readahead_hits_show, NULL); + +static ssize_t swap_readahead_total_show( + struct kobject *kobj, struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lld\n", percpu_counter_sum(&swapin_readahead_total)); +} +static struct kobj_attribute swap_readahead_total_attr = + __ATTR(ra_total, 0444, swap_readahead_total_show, NULL); + static struct attribute *swap_attrs[] = { &swap_cache_pages_attr.attr, &swap_cache_add_attr.attr, &swap_cache_del_attr.attr, &swap_cache_find_success_attr.attr, &swap_cache_find_total_attr.attr, + &swap_readahead_hits_attr.attr, + &swap_readahead_total_attr.attr, NULL, }; -- 2.13.2
