From: Kefeng Wang <wangkefeng.wang@huawei.com> maillist inclusion category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/I9JAY9 CVE: NA Reference: https://lore.kernel.org/linux-mm/20240418135644.2736748-1-wangkefeng.wang@hu... -------------------------------- Skip blk_cgroup_congested() if there is no usable swap device since no swapin/out will occur, Thereby avoid taking swap_lock. The difference is shown below from perf date of CoW pagefault, perf report -g -i perf.data.swapoff | egrep "blk_cgroup_congested|__folio_throttle_swaprate" 1.01% 0.16% page_fault2_pro [kernel.kallsyms] [k] __folio_throttle_swaprate 0.83% 0.80% page_fault2_pro [kernel.kallsyms] [k] blk_cgroup_congested perf report -g -i perf.data.swapon | egrep "blk_cgroup_congested|__folio_throttle_swaprate" 0.15% 0.15% page_fault2_pro [kernel.kallsyms] [k] __folio_throttle_swaprate Link: https://lkml.kernel.org/r/20240418135644.2736748-1-wangkefeng.wang@huawei.co... Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com> --- mm/swapfile.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 91f48df47952..3312f2422b36 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2465,13 +2465,17 @@ static void reinsert_swap_info(struct swap_info_struct *p) spin_unlock(&swap_lock); } +static bool __has_usable_swap(void) +{ + return !plist_head_empty(&swap_active_head); +} + bool has_usable_swap(void) { - bool ret = true; + bool ret; spin_lock(&swap_lock); - if (plist_head_empty(&swap_active_head)) - ret = false; + ret = __has_usable_swap(); spin_unlock(&swap_lock); return ret; } @@ -3728,6 +3732,9 @@ void __folio_throttle_swaprate(struct folio *folio, gfp_t gfp) if (!(gfp & __GFP_IO)) return; + if (!__has_usable_swap()) + return; + if (!blk_cgroup_congested()) return; -- 2.25.1