zram: implement rw_page operation of zram

This patch implements rw_page operation for zram block device.

I implemented the feature in zram and tested it.  Test bed was the G2, LG
electronic mobile device, whtich has msm8974 processor and 2GB memory.

With a memory allocation test program consuming memory, the system
generates swap.

Operating time of swap_write_page() was measured.

--------------------------------------------------
|             |   operating time   | improvement |
|             |  (20 runs average) |             |
--------------------------------------------------
|with patch   |    1061.15 us      |    +2.4%    |
--------------------------------------------------
|without patch|    1087.35 us      |             |
--------------------------------------------------

Each test(with paged_io,with BIO) result set shows normal distribution and
has equal variance.  I mean the two values are valid result to compare.  I
can say operation with paged I/O(without BIO) is faster 2.4% with
confidence level 95%.

[[email protected]: make rw_page opeartion return 0]
[[email protected]: rely on the bi_end_io for zram_rw_page fails]
[[email protected]: code cleanup]
[[email protected]: add comment]
Signed-off-by: karam.lee <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Jerome Marchand <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: <[email protected]>
Signed-off-by: Minchan Kim <[email protected]>
Signed-off-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions