diff options
| author | Vinayak Menon <vinmenon@codeaurora.org> | 2015-02-25 19:43:59 +0530 |
|---|---|---|
| committer | David Keitel <dkeitel@codeaurora.org> | 2016-03-22 11:03:52 -0700 |
| commit | e5ce54a9cbc60d691e15e8e72ec310ab99735906 (patch) | |
| tree | 4456aede35a36a68d20f89f6e4fece080583d9b4 /include | |
| parent | 0a8bf43567ab42f45f17773e53d623d746961743 (diff) | |
mm: swap: don't delay swap free for fast swap devices
There are couple of issues with swapcache usage when ZRAM is used
as swap device.
1) Kernel does a swap readahead which can be around 6 to 8 pages
depending on total ram, which is not required for zram since
accesses are fast.
2) Kernel delays the freeing up of swapcache expecting a later hit,
which again is useless in the case of zram.
3) This is not related to swapcache, but zram usage itself.
As mentioned in (2) kernel delays freeing of swapcache, but along with
that it delays zram compressed page free also. i.e. there can be 2 copies,
though one is compressed.
This patch addresses these issues using two new flags
QUEUE_FLAG_FAST and SWP_FAST, to indicate that accesses to the device
will be fast and cheap, and instructs the swap layer to free up
swap space agressively, and not to do read ahead.
Change-Id: I5d2d5176a5f9420300bb2f843f6ecbdb25ea80e4
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/blkdev.h | 2 | ||||
| -rw-r--r-- | include/linux/swap.h | 15 |
2 files changed, 14 insertions, 3 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 0adfa9e76f64..4c1110ed0881 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -489,6 +489,7 @@ struct request_queue { #define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */ #define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/ #define QUEUE_FLAG_POLL 22 /* IO polling enabled if set */ +#define QUEUE_FLAG_FAST 23 /* fast block device (e.g. ram based) */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ @@ -577,6 +578,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q) #define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags) #define blk_queue_secdiscard(q) (blk_queue_discard(q) && \ test_bit(QUEUE_FLAG_SECDISCARD, &(q)->queue_flags)) +#define blk_queue_fast(q) test_bit(QUEUE_FLAG_FAST, &(q)->queue_flags) #define blk_noretry_request(rq) \ ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \ diff --git a/include/linux/swap.h b/include/linux/swap.h index 7ba7dccaf0e7..b142d27b3edb 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -151,7 +151,8 @@ enum { SWP_AREA_DISCARD = (1 << 8), /* single-time swap area discards */ SWP_PAGE_DISCARD = (1 << 9), /* freed swap page-cluster discards */ /* add others here before... */ - SWP_SCANNING = (1 << 10), /* refcount in scan_swap_map */ + SWP_FAST = (1 << 10), /* blkdev access is fast and cheap */ + SWP_SCANNING = (1 << 11), /* refcount in scan_swap_map */ }; #define SWAP_CLUSTER_MAX 32UL @@ -415,10 +416,18 @@ extern struct page *swapin_readahead(swp_entry_t, gfp_t, /* linux/mm/swapfile.c */ extern atomic_long_t nr_swap_pages; extern long total_swap_pages; +extern bool is_swap_fast(swp_entry_t entry); /* Swap 50% full? Release swapcache more aggressively.. */ -static inline bool vm_swap_full(void) +static inline bool vm_swap_full(struct swap_info_struct *si) { + /* + * If the swap device is fast, return true + * not to delay swap free. + */ + if (si->flags & SWP_FAST) + return true; + return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages; } @@ -454,7 +463,7 @@ struct backing_dev_info; #define get_nr_swap_pages() 0L #define total_swap_pages 0L #define total_swapcache_pages() 0UL -#define vm_swap_full() 0 +#define vm_swap_full(si) 0 #define si_swapinfo(val) \ do { (val)->freeswap = (val)->totalswap = 0; } while (0) |