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authorMinchan Kim <minchan@kernel.org>2017-11-16 04:33:07 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-16 05:21:02 +0300
commit0bcac06f27d7528591c27ac2b093ccd71c5d0168 (patch)
treeb8261d05b232e57a58a7fe90306cad5d545de900 /mm/memory.c
parent539a6fea7fdcade532bd3e77be2862a683f8f0c9 (diff)
downloadlinux-0bcac06f27d7528591c27ac2b093ccd71c5d0168.tar.xz
mm, swap: skip swapcache for swapin of synchronous device
With fast swap storage, the platforms want to use swap more aggressively and swap-in is crucial to application latency. The rw_page() based synchronous devices like zram, pmem and btt are such fast storage. When I profile swapin performance with zram lz4 decompress test, S/W overhead is more than 70%. Maybe, it would be bigger in nvdimm. This patch aims to reduce swap-in latency by skipping swapcache if the swap device is synchronous device like rw_page based device. It enhances 45% my swapin test(5G sequential swapin, no readahead, from 2.41sec to 1.64sec). Link: http://lkml.kernel.org/r/1505886205-9671-5-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c52
1 files changed, 36 insertions, 16 deletions
diff --git a/mm/memory.c b/mm/memory.c
index cae514e7dcfc..f75bff2cf662 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2842,7 +2842,7 @@ EXPORT_SYMBOL(unmap_mapping_range);
int do_swap_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
- struct page *page = NULL, *swapcache;
+ struct page *page = NULL, *swapcache = NULL;
struct mem_cgroup *memcg;
struct vma_swap_readahead swap_ra;
swp_entry_t entry;
@@ -2881,17 +2881,35 @@ int do_swap_page(struct vm_fault *vmf)
}
goto out;
}
+
+
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
if (!page)
page = lookup_swap_cache(entry, vma_readahead ? vma : NULL,
vmf->address);
if (!page) {
- if (vma_readahead)
- page = do_swap_page_readahead(entry,
- GFP_HIGHUSER_MOVABLE, vmf, &swap_ra);
- else
- page = swapin_readahead(entry,
- GFP_HIGHUSER_MOVABLE, vma, vmf->address);
+ struct swap_info_struct *si = swp_swap_info(entry);
+
+ if (!(si->flags & SWP_SYNCHRONOUS_IO)) {
+ if (vma_readahead)
+ page = do_swap_page_readahead(entry,
+ GFP_HIGHUSER_MOVABLE, vmf, &swap_ra);
+ else
+ page = swapin_readahead(entry,
+ GFP_HIGHUSER_MOVABLE, vma, vmf->address);
+ swapcache = page;
+ } else {
+ /* skip swapcache */
+ page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address);
+ if (page) {
+ __SetPageLocked(page);
+ __SetPageSwapBacked(page);
+ set_page_private(page, entry.val);
+ lru_cache_add_anon(page);
+ swap_readpage(page, true);
+ }
+ }
+
if (!page) {
/*
* Back out if somebody else faulted in this pte
@@ -2920,7 +2938,6 @@ int do_swap_page(struct vm_fault *vmf)
goto out_release;
}
- swapcache = page;
locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);
delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
@@ -2935,7 +2952,8 @@ int do_swap_page(struct vm_fault *vmf)
* test below, are not enough to exclude that. Even if it is still
* swapcache, we need to check that the page's swap has not changed.
*/
- if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
+ if (unlikely((!PageSwapCache(page) ||
+ page_private(page) != entry.val)) && swapcache)
goto out_page;
page = ksm_might_need_to_copy(page, vma, vmf->address);
@@ -2988,14 +3006,16 @@ int do_swap_page(struct vm_fault *vmf)
pte = pte_mksoft_dirty(pte);
set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
vmf->orig_pte = pte;
- if (page == swapcache) {
- do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
- mem_cgroup_commit_charge(page, memcg, true, false);
- activate_page(page);
- } else { /* ksm created a completely new copy */
+
+ /* ksm created a completely new copy */
+ if (unlikely(page != swapcache && swapcache)) {
page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false, false);
lru_cache_add_active_or_unevictable(page, vma);
+ } else {
+ do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
+ mem_cgroup_commit_charge(page, memcg, true, false);
+ activate_page(page);
}
swap_free(entry);
@@ -3003,7 +3023,7 @@ int do_swap_page(struct vm_fault *vmf)
(vma->vm_flags & VM_LOCKED) || PageMlocked(page))
try_to_free_swap(page);
unlock_page(page);
- if (page != swapcache) {
+ if (page != swapcache && swapcache) {
/*
* Hold the lock to avoid the swap entry to be reused
* until we take the PT lock for the pte_same() check
@@ -3036,7 +3056,7 @@ out_page:
unlock_page(page);
out_release:
put_page(page);
- if (page != swapcache) {
+ if (page != swapcache && swapcache) {
unlock_page(swapcache);
put_page(swapcache);
}