swap readahead clean up

PATCH New Minchan Kim 1 participant 3 messages Nov 1, 2017

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Memory management MM core MM swap tmpfs (shmem filesystem)

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Minchan Kim

author

2017-11-01 07:15 UTC #0 lore raw

v2 cover swap readahead clean up

This patchset cleans up recent added vma-based readahead code via unifying cluster-based readahead.

* From v1
* renamed swap_cluster_readahead - Huang
* remove unnecessary extern declaration - Huang
* add description for swapin_readahead - Huang

Minchan Kim (2):
mm:swap: clean up swap readahead
mm:swap: unify cluster-based and vma-based swap readahead

 include/linux/swap.h |  38 +++-----------
 mm/memory.c          |  24 +++------
 mm/shmem.c           |   5 +-
 mm/swap_state.c      | 137 ++++++++++++++++++++++++++++++++-------------------
 4 files changed, 103 insertions(+), 101 deletions(-)

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Minchan Kim

author

2017-11-01 07:15 UTC #1 lore raw

PATCH v2 1/2 mm:swap: clean up swap readahead

When I see recent change of swap readahead, I am very unhappy about current code structure which diverges two swap readahead algorithm in do_swap_page. This patch is to clean it up.

Main motivation is that fault handler doesn't need to be aware of readahead algorithms but just should call swapin_readahead.

As first step, this patch cleans up a little bit but not perfect (I just separate for review easier) so next patch will make the goal complete.

Signed-off-by Minchan Kim <[email protected]>

---
 include/linux/swap.h | 17 ++--------
 mm/memory.c          | 17 +++-------
 mm/swap_state.c      | 89 ++++++++++++++++++++++++++++------------------------
 3 files changed, 55 insertions(+), 68 deletions(-)

include/linux/swap.h +3 ~~-14~~

index 84255b3da7c1..7c7c8b344bc9 100644
@@ -427,12 +427,8 @@ extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
 			bool *new_page_allocated);
 extern struct page *swapin_readahead(swp_entry_t, gfp_t,
 			struct vm_area_struct *vma, unsigned long addr);
-
-extern struct page *swap_readahead_detect(struct vm_fault *vmf,
-					  struct vma_swap_readahead *swap_ra);
 extern struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
-					   struct vm_fault *vmf,
-					   struct vma_swap_readahead *swap_ra);
+					   struct vm_fault *vmf);
 
 /* linux/mm/swapfile.c */
 extern atomic_long_t nr_swap_pages;

@@ -551,15 +547,8 @@ static inline bool swap_use_vma_readahead(void)
 	return false;
 }
 
-static inline struct page *swap_readahead_detect(
-	struct vm_fault *vmf, struct vma_swap_readahead *swap_ra)
-{
-	return NULL;
-}
-
-static inline struct page *do_swap_page_readahead(
-	swp_entry_t fentry, gfp_t gfp_mask,
-	struct vm_fault *vmf, struct vma_swap_readahead *swap_ra)
+static inline struct page *do_swap_page_readahead(swp_entry_t fentry,
+				gfp_t gfp_mask, struct vm_fault *vmf)
 {
 	return NULL;
 }

mm/memory.c +4 ~~-13~~

index 8a0c410037d2..e955298e4290 100644
@@ -2849,21 +2849,14 @@ int do_swap_page(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	struct page *page = NULL, *swapcache = NULL;
 	struct mem_cgroup *memcg;
-	struct vma_swap_readahead swap_ra;
 	swp_entry_t entry;
 	pte_t pte;
 	int locked;
 	int exclusive = 0;
 	int ret = 0;
-	bool vma_readahead = swap_use_vma_readahead();
 
-	if (vma_readahead)
-		page = swap_readahead_detect(vmf, &swap_ra);
-	if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) {
-		if (page)
-			put_page(page);
+	if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
 		goto out;
-	}
 
 	entry = pte_to_swp_entry(vmf->orig_pte);
 	if (unlikely(non_swap_entry(entry))) {

@@ -2889,9 +2882,7 @@ int do_swap_page(struct vm_fault *vmf)
 
 
 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
-	if (!page)
-		page = lookup_swap_cache(entry, vma_readahead ? vma : NULL,
-					 vmf->address);
+	page = lookup_swap_cache(entry, vma, vmf->address);
 	if (!page) {
 		struct swap_info_struct *si = swp_swap_info(entry);

@@ -2907,9 +2898,9 @@ int do_swap_page(struct vm_fault *vmf)
 				swap_readpage(page, true);
 			}
 		} else {
-			if (vma_readahead)
+			if (swap_use_vma_readahead())
 				page = do_swap_page_readahead(entry,
-					GFP_HIGHUSER_MOVABLE, vmf, &swap_ra);
+					GFP_HIGHUSER_MOVABLE, vmf);
 			else
 				page = swapin_readahead(entry,
 				       GFP_HIGHUSER_MOVABLE, vma, vmf->address);

mm/swap_state.c +48 ~~-41~~

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Minchan Kim

author

2017-11-01 07:15 UTC #2 lore raw

PATCH v2 2/2 mm:swap: unify cluster-based and vma-based swap readahead

In reply to Minchan Kim

This patch makes do_swap_page no need to be aware of two different swap readahead algorithm. Just unify cluster-based and vma-based readahead function call.

Signed-off-by Minchan Kim <[email protected]>

---
 include/linux/swap.h | 27 ++++++++-------------------
 mm/memory.c          | 11 ++++-------
 mm/shmem.c           |  5 ++++-
 mm/swap_state.c      | 48 +++++++++++++++++++++++++++++++++++++-----------
 4 files changed, 53 insertions(+), 38 deletions(-)

include/linux/swap.h +8 ~~-19~~

index 7c7c8b344bc9..95fca979b1c1 100644
@@ -403,7 +403,6 @@ int generic_swapfile_activate(struct swap_info_struct *, struct file *,
 #define SWAP_ADDRESS_SPACE_SHIFT	14
 #define SWAP_ADDRESS_SPACE_PAGES	(1 << SWAP_ADDRESS_SPACE_SHIFT)
 extern struct address_space *swapper_spaces[];
-extern bool swap_vma_readahead;
 #define swap_address_space(entry)			    \
 	(&swapper_spaces[swp_type(entry)][swp_offset(entry) \
 		>> SWAP_ADDRESS_SPACE_SHIFT])

@@ -425,10 +424,10 @@ extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
 extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
 			struct vm_area_struct *vma, unsigned long addr,
 			bool *new_page_allocated);
-extern struct page *swapin_readahead(swp_entry_t, gfp_t,
-			struct vm_area_struct *vma, unsigned long addr);
-extern struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
-					   struct vm_fault *vmf);
+extern struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
+				struct vm_fault *vmf);
+extern struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
+				struct vm_fault *vmf);
 
 /* linux/mm/swapfile.c */
 extern atomic_long_t nr_swap_pages;

@@ -436,11 +435,6 @@ extern long total_swap_pages;
 extern atomic_t nr_rotate_swap;
 extern bool has_usable_swap(void);
 
-static inline bool swap_use_vma_readahead(void)
-{
-	return READ_ONCE(swap_vma_readahead) && !atomic_read(&nr_rotate_swap);
-}
-
 /* Swap 50% full? Release swapcache more aggressively.. */
 static inline bool vm_swap_full(void)
 {

@@ -536,19 +530,14 @@ static inline void put_swap_page(struct page *page, swp_entry_t swp)
 {
 }
 
-static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
-			struct vm_area_struct *vma, unsigned long addr)
+static inline struct page *swap_cluster_readahead(swp_entry_t entry,
+				gfp_t gfp_mask, struct vm_fault *vmf)
 {
 	return NULL;
 }
 
-static inline bool swap_use_vma_readahead(void)
-{
-	return false;
-}
-
-static inline struct page *do_swap_page_readahead(swp_entry_t fentry,
-				gfp_t gfp_mask, struct vm_fault *vmf)
+static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
+			struct vm_fault *vmf)
 {
 	return NULL;
 }

mm/memory.c +4 -7

index e955298e4290..ce5e3d7ccc5c 100644
@@ -2889,7 +2889,8 @@ int do_swap_page(struct vm_fault *vmf)
 		if (si->flags & SWP_SYNCHRONOUS_IO &&
 				__swap_count(si, entry) == 1) {
 			/* skip swapcache */
-			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address);
+			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
+							vmf->address);
 			if (page) {
 				__SetPageLocked(page);
 				__SetPageSwapBacked(page);

@@ -2898,12 +2899,8 @@ int do_swap_page(struct vm_fault *vmf)
 				swap_readpage(page, true);
 			}
 		} else {
-			if (swap_use_vma_readahead())
-				page = do_swap_page_readahead(entry,
-					GFP_HIGHUSER_MOVABLE, vmf);
-			else
-				page = swapin_readahead(entry,
-				       GFP_HIGHUSER_MOVABLE, vma, vmf->address);
+			page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
+						vmf);
 			swapcache = page;
 		}

mm/shmem.c +4 -1

index 62dfdc097e44..d92923834d68 100644
@@ -1413,9 +1413,12 @@ static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 {
 	struct vm_area_struct pvma;
 	struct page *page;
+	struct vm_fault vmf;
 
 	shmem_pseudo_vma_init(&pvma, info, index);
-	page = swapin_readahead(swap, gfp, &pvma, 0);
+	vmf.vma = &pvma;
+	vmf.address = 0;
+	page = swap_cluster_readahead(swap, gfp, &vmf);
 	shmem_pseudo_vma_destroy(&pvma);
 
 	return page;

mm/swap_state.c +37 ~~-11~~

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