From: Kairui Song <kasong@xxxxxxxxxxx>
Currently VMA readahead is globally disabled when any rotate disk is
used as swap backend. So multiple swap devices are enabled, if a slower
hard disk is set as a low priority fallback, and a high performance SSD
is used and high priority swap device, vma readahead is disabled globally.
The SSD swap device performance will drop by a lot.
Check readahead policy per entry to avoid such problem.
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
mm/swap_state.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ff6756f2e8e4..fb78f7f18ed7 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -321,9 +321,9 @@ static inline bool swap_use_no_readahead(struct swap_info_struct *si, swp_entry_
return data_race(si->flags & SWP_SYNCHRONOUS_IO) && __swap_count(entry) == 1;
}
-static inline bool swap_use_vma_readahead(void)
+static inline bool swap_use_vma_readahead(struct swap_info_struct *si)
{
- return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
+ return data_race(si->flags & SWP_SOLIDSTATE) && READ_ONCE(enable_vma_readahead);
}
/*
@@ -341,7 +341,7 @@ struct folio *swap_cache_get_folio(swp_entry_t entry,
folio = filemap_get_folio(swap_address_space(entry), swp_offset(entry));
if (!IS_ERR(folio)) {
- bool vma_ra = swap_use_vma_readahead();
+ bool vma_ra = swap_use_vma_readahead(swp_swap_info(entry));
bool readahead;
/*
@@ -920,16 +920,18 @@ static struct page *swapin_no_readahead(swp_entry_t entry, gfp_t gfp_mask,
struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
struct vm_fault *vmf, bool *swapcached)
{
+ struct swap_info_struct *si;
struct mempolicy *mpol;
struct page *page;
pgoff_t ilx;
bool cached;
+ si = swp_swap_info(entry);
mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx);
- if (swap_use_no_readahead(swp_swap_info(entry), entry)) {
+ if (swap_use_no_readahead(si, entry)) {
page = swapin_no_readahead(entry, gfp_mask, mpol, ilx, vmf->vma->vm_mm);
cached = false;
- } else if (swap_use_vma_readahead()) {
+ } else if (swap_use_vma_readahead(si)) {
page = swap_vma_readahead(entry, gfp_mask, mpol, ilx, vmf);
cached = true;
} else {
--
2.42.0
