writeback: fix occasional slow sync(1)

In case when system contains no dirty pages, wakeup_flusher_threads() will
submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits
immediately without doing anything, even though there are dirty inodes in
the system.  Thus sync(1) will write all the dirty inodes from a
WB_SYNC_ALL writeback pass which is slow.

Fix the problem by using get_nr_dirty_pages() in wakeup_flusher_threads()
instead of calculating number of dirty pages manually.  That function also
takes number of dirty inodes into account.

Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Paul Taysom <taysom@chromium.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
block: Allow 0ms deadline latency, increase the read speed
 Change a timer compare from after to after-equals, thus allowing 0 timeout
 and making deadline, sio and zen schedulers FIFO.

Signed-off-by: xiaobing tu <xiaobing.tu@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Fix zram compiling error
Optimize SLUB
bcmdhd: update drivers 1.61.47 --> 1.61.58
sched: LOAD_FREQ (4*HZ+61) avoids loadavg Moire. From http://ripke.co…
…m/loadavg/moire
cpufreq: boostpulse for ondemand based governors
This is based on Steve Kondik's patch for ondemand, extended for multiple governors.

Signed-off-by: Gustavo Santos <gustavo.santos0106@gmail.com>