On Thu, 21 Sep 2023 20:27:51 +0800 Jiexun Wang <wangjiexun@xxxxxxxxxxx> wrote:
> Currently the madvise_cold_or_pageout_pte_range() function exhibits
> significant latency under memory pressure, which can be effectively
> reduced by adding cond_resched() within the loop.
>
> When the batch_count reaches SWAP_CLUSTER_MAX, we reschedule
> the task to ensure fairness and avoid long lock holding times.
>
> ...
>
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -354,6 +354,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> struct folio *folio = NULL;
> LIST_HEAD(folio_list);
> bool pageout_anon_only_filter;
> + unsigned int batch_count = 0;
>
> if (fatal_signal_pending(current))
> return -EINTR;
> @@ -433,6 +434,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> regular_folio:
> #endif
> tlb_change_page_size(tlb, PAGE_SIZE);
> +restart:
> start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
The handling of start_pte looks OK.
> if (!start_pte)
> return 0;
> @@ -441,6 +443,15 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> for (; addr < end; pte++, addr += PAGE_SIZE) {
> ptent = ptep_get(pte);
>
> + if (++batch_count == SWAP_CLUSTER_MAX) {
> + batch_count = 0;
> + if (need_resched()) {
> + pte_unmap_unlock(start_pte, ptl);
> + cond_resched();
> + goto restart;
> + }
> + }
> +
> if (pte_none(ptent))
> continue;
>
I think this patch looks OK, but would appreciate careful review from
others, please.
