mm: swapfile: check usable swap device in __folio_throttle_swaprate()
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.swapon | 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.swapoff | 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.com Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -2444,13 +2444,17 @@ static void reinsert_swap_info(struct swap_info_struct *p)
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spin_unlock(&swap_lock);
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}
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static bool __has_usable_swap(void)
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{
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return !plist_head_empty(&swap_active_head);
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}
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bool has_usable_swap(void)
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{
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bool ret = true;
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bool ret;
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spin_lock(&swap_lock);
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if (plist_head_empty(&swap_active_head))
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ret = false;
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ret = __has_usable_swap();
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spin_unlock(&swap_lock);
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return ret;
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}
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@ -3710,6 +3714,9 @@ void __folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
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if (!(gfp & __GFP_IO))
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return;
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if (!__has_usable_swap())
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return;
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if (!blk_cgroup_congested())
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return;
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