On Mon, Jun 03, 2019 at 02:36:55PM +0900, Minchan Kim wrote: > When a process expects no accesses to a certain memory range > for a long time, it could hint kernel that the pages can be > reclaimed instantly but data should be preserved for future use. > This could reduce workingset eviction so it ends up increasing > performance. > > This patch introduces the new MADV_PAGEOUT hint to madvise(2) > syscall. MADV_PAGEOUT can be used by a process to mark a memory > range as not expected to be used for a long time so that kernel > reclaims *any LRU* pages instantly. The hint can help kernel in deciding > which pages to evict proactively. > > All of error rule is same with MADV_DONTNEED. > > Note: > This hint works with only private pages(IOW, page_mapcount(page) < 2) > because shared page could have more chance to be accessed from other > processes sharing the page so that it could cause major fault soon, > which is inefficient. > > * RFC v2 > * make reclaim_pages simple via factoring out isolate logic - hannes > > * RFCv1 > * rename from MADV_COLD to MADV_PAGEOUT - hannes > * bail out if process is being killed - Hillf > * fix reclaim_pages bugs - Hillf > > Signed-off-by: Minchan Kim <minc...@kernel.org> > --- > include/linux/swap.h | 1 + > include/uapi/asm-generic/mman-common.h | 1 + > mm/madvise.c | 126 +++++++++++++++++++++++++ > mm/vmscan.c | 34 +++++++ > 4 files changed, 162 insertions(+) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 0ce997edb8bb..063c0c1e112b 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -365,6 +365,7 @@ extern int vm_swappiness; > extern int remove_mapping(struct address_space *mapping, struct page *page); > extern unsigned long vm_total_pages; > > +extern unsigned long reclaim_pages(struct list_head *page_list); > #ifdef CONFIG_NUMA > extern int node_reclaim_mode; > extern int sysctl_min_unmapped_ratio; > diff --git a/include/uapi/asm-generic/mman-common.h > b/include/uapi/asm-generic/mman-common.h > index 1190f4e7f7b9..92e347a89ddc 100644 > --- a/include/uapi/asm-generic/mman-common.h > +++ b/include/uapi/asm-generic/mman-common.h > @@ -44,6 +44,7 @@ > #define MADV_WILLNEED 3 /* will need these pages */ > #define MADV_DONTNEED 4 /* don't need these pages */ > #define MADV_COLD 5 /* deactivatie these pages */ > +#define MADV_PAGEOUT 6 /* reclaim these pages */ > > /* common parameters: try to keep these consistent across architectures */ > #define MADV_FREE 8 /* free pages only if memory pressure */ > diff --git a/mm/madvise.c b/mm/madvise.c > index ab158766858a..b010249cb8b6 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -41,6 +41,7 @@ static int madvise_need_mmap_write(int behavior) > case MADV_WILLNEED: > case MADV_DONTNEED: > case MADV_COLD: > + case MADV_PAGEOUT: > case MADV_FREE: > return 0; > default: > @@ -415,6 +416,128 @@ static long madvise_cold(struct vm_area_struct *vma, > return 0; > } > > +static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr, > + unsigned long end, struct mm_walk *walk) > +{ > + pte_t *orig_pte, *pte, ptent; > + spinlock_t *ptl; > + LIST_HEAD(page_list); > + struct page *page; > + int isolated = 0; > + struct vm_area_struct *vma = walk->vma; > + unsigned long next; > + > + if (fatal_signal_pending(current)) > + return -EINTR; > + > + next = pmd_addr_end(addr, end); > + if (pmd_trans_huge(*pmd)) { > + ptl = pmd_trans_huge_lock(pmd, vma); > + if (!ptl) > + return 0; > + > + if (is_huge_zero_pmd(*pmd)) > + goto huge_unlock; > + > + page = pmd_page(*pmd); > + if (page_mapcount(page) > 1) > + goto huge_unlock; > + > + if (next - addr != HPAGE_PMD_SIZE) { > + int err; > + > + get_page(page); > + spin_unlock(ptl); > + lock_page(page); > + err = split_huge_page(page); > + unlock_page(page); > + put_page(page); > + if (!err) > + goto regular_page; > + return 0; > + } > + > + if (isolate_lru_page(page)) > + goto huge_unlock; > + > + list_add(&page->lru, &page_list); > +huge_unlock: > + spin_unlock(ptl); > + reclaim_pages(&page_list); > + return 0; > + } > + > + if (pmd_trans_unstable(pmd)) > + return 0; > +regular_page: > + orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); > + for (pte = orig_pte; addr < end; pte++, addr += PAGE_SIZE) { > + ptent = *pte; > + if (!pte_present(ptent)) > + continue; > + > + page = vm_normal_page(vma, addr, ptent); > + if (!page) > + continue; > + > + if (page_mapcount(page) > 1) > + continue; > + > + if (isolate_lru_page(page)) > + continue; > + > + isolated++; > + list_add(&page->lru, &page_list); > + if (isolated >= SWAP_CLUSTER_MAX) { > + pte_unmap_unlock(orig_pte, ptl); > + reclaim_pages(&page_list); > + isolated = 0; > + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); > + orig_pte = pte; > + } > + } > + > + pte_unmap_unlock(orig_pte, ptl); > + reclaim_pages(&page_list); > + cond_resched(); > + > + return 0; > +} > + > +static void madvise_pageout_page_range(struct mmu_gather *tlb, > + struct vm_area_struct *vma, > + unsigned long addr, unsigned long end) > +{ > + struct mm_walk warm_walk = { > + .pmd_entry = madvise_pageout_pte_range, > + .mm = vma->vm_mm, > + }; > + > + tlb_start_vma(tlb, vma); > + walk_page_range(addr, end, &warm_walk); > + tlb_end_vma(tlb, vma); > +} > + > + > +static long madvise_pageout(struct vm_area_struct *vma, > + struct vm_area_struct **prev, > + unsigned long start_addr, unsigned long end_addr) > +{ > + struct mm_struct *mm = vma->vm_mm; > + struct mmu_gather tlb; > + > + *prev = vma; > + if (!can_madv_lru_vma(vma)) > + return -EINVAL; > + > + lru_add_drain(); > + tlb_gather_mmu(&tlb, mm, start_addr, end_addr); > + madvise_pageout_page_range(&tlb, vma, start_addr, end_addr); > + tlb_finish_mmu(&tlb, start_addr, end_addr); > + > + return 0; > +} > + > static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, > unsigned long end, struct mm_walk *walk) > > @@ -805,6 +928,8 @@ madvise_vma(struct vm_area_struct *vma, struct > vm_area_struct **prev, > return madvise_willneed(vma, prev, start, end); > case MADV_COLD: > return madvise_cold(vma, prev, start, end); > + case MADV_PAGEOUT: > + return madvise_pageout(vma, prev, start, end); > case MADV_FREE: > case MADV_DONTNEED: > return madvise_dontneed_free(vma, prev, start, end, behavior); > @@ -827,6 +952,7 @@ madvise_behavior_valid(int behavior) > case MADV_DONTNEED: > case MADV_FREE: > case MADV_COLD: > + case MADV_PAGEOUT: > #ifdef CONFIG_KSM > case MADV_MERGEABLE: > case MADV_UNMERGEABLE: > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 56df55e8afcd..2c2cf442db58 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2136,6 +2136,40 @@ static void shrink_active_list(unsigned long > nr_to_scan, > nr_deactivate, nr_rotated, sc->priority, file); > } > > +unsigned long reclaim_pages(struct list_head *page_list) > +{ > + unsigned long nr_reclaimed = 0; > + LIST_HEAD(node_page_list); > + struct reclaim_stat dummy_stat; > + struct scan_control sc = { > + .gfp_mask = GFP_KERNEL, > + .priority = DEF_PRIORITY, > + .may_writepage = 1, > + .may_unmap = 1, > + .may_swap = 1, > + }; > + > + while (!list_empty(page_list)) { > + struct page *page; > + > + page = lru_to_page(page_list); > + list_move(&page->lru, &node_page_list); > + nr_reclaimed += shrink_page_list(&node_page_list, > + page_pgdat(page), > + &sc, TTU_IGNORE_ACCESS, > + &dummy_stat, true); > + if (!list_empty(&node_page_list)) { > + struct page *page = lru_to_page(&node_page_list); > + > + list_del(&page->lru); > + putback_lru_page(page); > + > + } > + }
Awesome, this is way more readable now. Thanks for the cleanup! Regarding the loop, for the vast majority of instances, pages on page_list will actually be from the same node. It would make sense to do batching here and collect pages until last_pgdat != pgdat. That should reduce the number of tlb flushes and memcg uncharge flushes in shrink_page_list().