linux/include
Tejun Heo 839a8e8660 writeback: replace custom worker pool implementation with unbound workqueue
Writeback implements its own worker pool - each bdi can be associated
with a worker thread which is created and destroyed dynamically.  The
worker thread for the default bdi is always present and serves as the
"forker" thread which forks off worker threads for other bdis.

there's no reason for writeback to implement its own worker pool when
using unbound workqueue instead is much simpler and more efficient.
This patch replaces custom worker pool implementation in writeback
with an unbound workqueue.

The conversion isn't too complicated but the followings are worth
mentioning.

* bdi_writeback->last_active, task and wakeup_timer are removed.
  delayed_work ->dwork is added instead.  Explicit timer handling is
  no longer necessary.  Everything works by either queueing / modding
  / flushing / canceling the delayed_work item.

* bdi_writeback_thread() becomes bdi_writeback_workfn() which runs off
  bdi_writeback->dwork.  On each execution, it processes
  bdi->work_list and reschedules itself if there are more things to
  do.

  The function also handles low-mem condition, which used to be
  handled by the forker thread.  If the function is running off a
  rescuer thread, it only writes out limited number of pages so that
  the rescuer can serve other bdis too.  This preserves the flusher
  creation failure behavior of the forker thread.

* INIT_LIST_HEAD(&bdi->bdi_list) is used to tell
  bdi_writeback_workfn() about on-going bdi unregistration so that it
  always drains work_list even if it's running off the rescuer.  Note
  that the original code was broken in this regard.  Under memory
  pressure, a bdi could finish unregistration with non-empty
  work_list.

* The default bdi is no longer special.  It now is treated the same as
  any other bdi and bdi_cap_flush_forker() is removed.

* BDI_pending is no longer used.  Removed.

* Some tracepoints become non-applicable.  The following TPs are
  removed - writeback_nothread, writeback_wake_thread,
  writeback_wake_forker_thread, writeback_thread_start,
  writeback_thread_stop.

Everything, including devices coming and going away and rescuer
operation under simulated memory pressure, seems to work fine in my
test setup.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
2013-04-01 19:08:06 -07:00
..
acpi Fixes: 2013-03-12 20:25:53 -07:00
asm-generic asm-generic: move cmpxchg*_local defs to cmpxchg.h 2013-03-13 06:11:05 +01:00
clocksource ImgTec Meta architecture changes for v3.9-rc1 2013-03-03 12:06:09 -08:00
crypto
drm drm/radeon: add Richland pci ids 2013-03-15 18:47:19 -04:00
keys
linux writeback: replace custom worker pool implementation with unbound workqueue 2013-04-01 19:08:06 -07:00
math-emu
media [media] media: ov7670: Add possibility to disable pixclk during hblank 2013-02-08 14:35:06 -02:00
memory
misc
net ipv4: Fix ip-header identification for gso packets. 2013-03-26 13:50:05 -04:00
pcmcia
ras edac: add support for error type "Info" 2013-02-21 14:16:27 -03:00
rdma IB/core: Add "type 2" memory windows support 2013-02-21 11:51:45 -08:00
rxrpc
scsi SCSI for-linus on 20130301 2013-03-02 11:42:16 -08:00
sound arm-soc: late OMAP changes 2013-02-28 20:00:40 -08:00
target target: Rename spc_get_write_same_sectors -> sbc_get_write_same_sectors 2013-02-23 12:46:14 -08:00
trace writeback: replace custom worker pool implementation with unbound workqueue 2013-04-01 19:08:06 -07:00
uapi net: fix *_DIAG_MAX constants 2013-03-21 12:36:33 -04:00
video ARM: at91: fix LCD-wiring mode 2013-03-13 11:05:04 +01:00
xen for-linus-20130331 2013-03-31 11:38:59 -07:00
Kbuild