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mm, swap: skip swapcache for swapin of synchronous device

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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>
This commit is contained in:
Minchan Kim
2017-11-15 17:33:07 -08:00
committed by Linus Torvalds
parent 539a6fea7f
commit 0bcac06f27
4 changed files with 57 additions and 23 deletions
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11
mm/swapfile.c
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@@ -3455,10 +3455,15 @@ int swapcache_prepare(swp_entry_t entry)
return __swap_duplicate(entry, SWAP_HAS_CACHE);
}
struct swap_info_struct *swp_swap_info(swp_entry_t entry)
{
return swap_info[swp_type(entry)];
}
struct swap_info_struct *page_swap_info(struct page *page)
{
swp_entry_t swap = { .val = page_private(page) };
return swap_info[swp_type(swap)];
swp_entry_t entry = { .val = page_private(page) };
return swp_swap_info(entry);
}
/*
@@ -3466,7 +3471,6 @@ struct swap_info_struct *page_swap_info(struct page *page)
*/
struct address_space *__page_file_mapping(struct page *page)
{
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
return page_swap_info(page)->swap_file->f_mapping;
}
EXPORT_SYMBOL_GPL(__page_file_mapping);
@@ -3474,7 +3478,6 @@ EXPORT_SYMBOL_GPL(__page_file_mapping);
pgoff_t __page_file_index(struct page *page)
{
swp_entry_t swap = { .val = page_private(page) };
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
return swp_offset(swap);
}
EXPORT_SYMBOL_GPL(__page_file_index);