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Message-ID: <87jznrgvp7.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Tue, 30 Jan 2024 14:51:48 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Kairui Song <ryncsn@...il.com>
Cc: linux-mm@...ck.org, Kairui Song <kasong@...cent.com>, Andrew Morton
<akpm@...ux-foundation.org>, Chris Li <chrisl@...nel.org>, Hugh Dickins
<hughd@...gle.com>, Johannes Weiner <hannes@...xchg.org>, Matthew Wilcox
<willy@...radead.org>, Michal Hocko <mhocko@...e.com>, Yosry Ahmed
<yosryahmed@...gle.com>, David Hildenbrand <david@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/7] mm/swap: avoid a duplicated swap cache lookup
for SWP_SYNCHRONOUS_IO
Kairui Song <ryncsn@...il.com> writes:
> From: Kairui Song <kasong@...cent.com>
>
> When a xa_value is returned by the cache lookup, keep it to be used
> later for workingset refault check instead of doing the looking up again
> in swapin_no_readahead.
>
> Shadow look up and workingset check is skipped for swapoff to reduce
> overhead, workingset checking for anon pages upon swapoff is not
> helpful, simply consider all pages as inactive make more sense since
> swapoff doesn't mean pages is being accessed.
>
> After this commit, swappin is about 4% faster for ZRAM, micro benchmark
> result which use madvise to swap out 10G zero-filled data to ZRAM then
> read them in:
>
> Before: 11143285 us
> After: 10692644 us (+4.1%)
>
> Signed-off-by: Kairui Song <kasong@...cent.com>
LGTM, Thanks!
Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
> ---
> mm/memory.c | 5 +++--
> mm/shmem.c | 2 +-
> mm/swap.h | 11 ++++++-----
> mm/swap_state.c | 23 +++++++++++++----------
> mm/swapfile.c | 4 ++--
> 5 files changed, 25 insertions(+), 20 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 8711f8a07039..349946899f8d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3800,6 +3800,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> struct swap_info_struct *si = NULL;
> rmap_t rmap_flags = RMAP_NONE;
> bool exclusive = false;
> + void *shadow = NULL;
> swp_entry_t entry;
> pte_t pte;
> vm_fault_t ret = 0;
> @@ -3858,14 +3859,14 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> if (unlikely(!si))
> goto out;
>
> - folio = swap_cache_get_folio(entry, vma, vmf->address);
> + folio = swap_cache_get_folio(entry, vma, vmf->address, &shadow);
> if (folio)
> page = folio_file_page(folio, swp_offset(entry));
> swapcache = folio;
>
> if (!folio) {
> folio = swapin_entry(entry, GFP_HIGHUSER_MOVABLE,
> - vmf, &swapcache);
> + vmf, &swapcache, shadow);
> if (!folio) {
> /*
> * Back out if somebody else faulted in this pte
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d7c84ff62186..698a31bf7baa 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1873,7 +1873,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
> }
>
> /* Look it up and read it in.. */
> - folio = swap_cache_get_folio(swap, NULL, 0);
> + folio = swap_cache_get_folio(swap, NULL, 0, NULL);
> if (!folio) {
> /* Or update major stats only when swapin succeeds?? */
> if (fault_type) {
> diff --git a/mm/swap.h b/mm/swap.h
> index 8f8185d3865c..ca9cb472a263 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -42,7 +42,8 @@ void delete_from_swap_cache(struct folio *folio);
> void clear_shadow_from_swap_cache(int type, unsigned long begin,
> unsigned long end);
> struct folio *swap_cache_get_folio(swp_entry_t entry,
> - struct vm_area_struct *vma, unsigned long addr);
> + struct vm_area_struct *vma, unsigned long addr,
> + void **shadowp);
> struct folio *filemap_get_incore_folio(struct address_space *mapping,
> pgoff_t index);
>
> @@ -54,8 +55,8 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_flags,
> bool skip_if_exists);
> struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
> struct mempolicy *mpol, pgoff_t ilx);
> -struct folio *swapin_entry(swp_entry_t entry, gfp_t flag,
> - struct vm_fault *vmf, struct folio **swapcached);
> +struct folio *swapin_entry(swp_entry_t entry, gfp_t flag, struct vm_fault *vmf,
> + struct folio **swapcached, void *shadow);
>
> static inline unsigned int folio_swap_flags(struct folio *folio)
> {
> @@ -87,7 +88,7 @@ static inline struct folio *swap_cluster_readahead(swp_entry_t entry,
> }
>
> static inline struct folio *swapin_entry(swp_entry_t swp, gfp_t gfp_mask,
> - struct vm_fault *vmf, struct folio **swapcached)
> + struct vm_fault *vmf, struct folio **swapcached, void *shadow)
> {
> return NULL;
> }
> @@ -98,7 +99,7 @@ static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
> }
>
> static inline struct folio *swap_cache_get_folio(swp_entry_t entry,
> - struct vm_area_struct *vma, unsigned long addr)
> + struct vm_area_struct *vma, unsigned long addr, void **shadowp)
> {
> return NULL;
> }
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 5e06b2e140d4..e41a137a6123 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -330,12 +330,18 @@ static inline bool swap_use_vma_readahead(void)
> * Caller must lock the swap device or hold a reference to keep it valid.
> */
> struct folio *swap_cache_get_folio(swp_entry_t entry,
> - struct vm_area_struct *vma, unsigned long addr)
> + struct vm_area_struct *vma, unsigned long addr, void **shadowp)
> {
> struct folio *folio;
>
> - folio = filemap_get_folio(swap_address_space(entry), swp_offset(entry));
> - if (!IS_ERR(folio)) {
> + folio = filemap_get_entry(swap_address_space(entry), swp_offset(entry));
> + if (xa_is_value(folio)) {
> + if (shadowp)
> + *shadowp = folio;
> + return NULL;
> + }
> +
> + if (folio) {
> bool vma_ra = swap_use_vma_readahead();
> bool readahead;
>
> @@ -365,8 +371,6 @@ struct folio *swap_cache_get_folio(swp_entry_t entry,
> if (!vma || !vma_ra)
> atomic_inc(&swapin_readahead_hits);
> }
> - } else {
> - folio = NULL;
> }
>
> return folio;
> @@ -866,16 +870,16 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> * @entry: swap entry of this memory
> * @gfp_mask: memory allocation flags
> * @vmf: fault information
> + * @shadow: workingset shadow corresponding to entry
> *
> * Returns the struct folio for entry and addr after the swap entry is read
> * in.
> */
> static struct folio *swapin_direct(swp_entry_t entry, gfp_t gfp_mask,
> - struct vm_fault *vmf)
> + struct vm_fault *vmf, void *shadow)
> {
> struct vm_area_struct *vma = vmf->vma;
> struct folio *folio;
> - void *shadow = NULL;
>
> /* skip swapcache */
> folio = vma_alloc_folio(gfp_mask, 0,
> @@ -892,7 +896,6 @@ static struct folio *swapin_direct(swp_entry_t entry, gfp_t gfp_mask,
> }
> mem_cgroup_swapin_uncharge_swap(entry);
>
> - shadow = get_shadow_from_swap_cache(entry);
> if (shadow)
> workingset_refault(folio, shadow);
>
> @@ -922,7 +925,7 @@ static struct folio *swapin_direct(swp_entry_t entry, gfp_t gfp_mask,
> * or skip the readahead(ie, ramdisk based swap device).
> */
> struct folio *swapin_entry(swp_entry_t entry, gfp_t gfp_mask,
> - struct vm_fault *vmf, struct folio **swapcache)
> + struct vm_fault *vmf, struct folio **swapcache, void *shadow)
> {
> struct mempolicy *mpol;
> struct folio *folio;
> @@ -930,7 +933,7 @@ struct folio *swapin_entry(swp_entry_t entry, gfp_t gfp_mask,
>
> if (data_race(swp_swap_info(entry)->flags & SWP_SYNCHRONOUS_IO) &&
> __swap_count(entry) == 1) {
> - folio = swapin_direct(entry, gfp_mask, vmf);
> + folio = swapin_direct(entry, gfp_mask, vmf, shadow);
> } else {
> mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx);
> if (swap_use_vma_readahead())
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 1cf7e72e19e3..aac26f5a6cec 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1865,7 +1865,7 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> pte_unmap(pte);
> pte = NULL;
>
> - folio = swap_cache_get_folio(entry, vma, addr);
> + folio = swap_cache_get_folio(entry, vma, addr, NULL);
> if (!folio) {
> struct vm_fault vmf = {
> .vma = vma,
> @@ -1875,7 +1875,7 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> };
>
> folio = swapin_entry(entry, GFP_HIGHUSER_MOVABLE,
> - &vmf, NULL);
> + &vmf, NULL, NULL);
> }
> if (!folio) {
> /*
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