linux.git/fs/btrfs/async-thread.c, branch v2.6.30

Btrfs: add a priority queue to the async thread helpers

2009-04-20T19:53:08+00:00

Btrfs is using WRITE_SYNC_PLUG to send down synchronous IOs with a
higher priority.  But, the checksumming helper threads prevent it
from being fully effective.

There are two problems.  First, a big queue of pending checksumming
will delay the synchronous IO behind other lower priority writes.  Second,
the checksumming uses an ordered async work queue.  The ordering makes sure
that IOs are sent to the block layer in the same order they are sent
to the checksumming threads.  Usually this gives us less seeky IO.

But, when we start mixing IO priorities, the lower priority IO can delay
the higher priority IO.

This patch solves both problems by adding a high priority list to the async
helper threads, and a new btrfs_set_work_high_prio(), which is used
to make put a new async work item onto the higher priority list.

The ordering is still done on high priority IO, but all of the high
priority bios are ordered separately from the low priority bios.  This
ordering is purely an IO optimization, it is not involved in data
or metadata integrity.

Signed-off-by: Chris Mason

Btrfs: remove unused ftrace include

2009-04-02T21:02:55+00:00

Signed-off-by: jim owens 
Signed-off-by: Chris Mason

Btrfs: fix race in worker_loop

2009-04-02T21:01:27+00:00

Need to check kthread_should_stop after schedule_timeout() before calling
schedule(). This causes threads to sleep with potentially no one to wake them
up causing mount(2) to hang in btrfs_stop_workers waiting for threads to stop.

Signed-off-by: Amit Gud 
Signed-off-by: Chris Mason

Btrfs: async threads should try harder to find work

2009-02-04T14:23:24+00:00

Tracing shows the delay between when an async thread goes to sleep
and when more work is added is often very short.  This commit adds
a little bit of delay and extra checking to the code right before
we schedule out.

It allows more work to be added to the worker
without requiring notifications from other procs.

Signed-off-by: Chris Mason

Btrfs: Catch missed bios in the async bio submission thread

2009-02-04T14:19:41+00:00

The async bio submission thread was missing some bios that were
added after it had decided there was no work left to do.

Signed-off-by: Chris Mason

Btrfs: removed unused #include 's

2009-01-21T15:49:16+00:00

Removed unused #include 's in btrfs

Signed-off-by: Huang Weiyi 
Signed-off-by: Chris Mason

Btrfs: Fix checkpatch.pl warnings

2009-01-06T02:25:51+00:00

There were many, most are fixed now.  struct-funcs.c generates some warnings
but these are bogus.

Signed-off-by: Chris Mason

Btrfs: Check kthread_should_stop() before schedule() in worker_loop

2008-11-12T19:36:58+00:00

In worker_loop(), the func should check whether it has been requested to stop
before it decides to schedule out.

Otherwise if the stop request(also the last wake_up()) sent by
btrfs_stop_workers() happens when worker_loop() running after the "while"
judgement and before schedule(), woker_loop() will schedule away and never be
woken up, which will also cause btrfs_stop_workers() wait forever.

Signed-off-by: Chris Mason

Btrfs: Add ordered async work queues

2008-11-07T03:03:00+00:00

Btrfs uses kernel threads to create async work queues for cpu intensive
operations such as checksumming and decompression.  These work well,
but they make it difficult to keep IO order intact.

A single writepages call from pdflush or fsync will turn into a number
of bios, and each bio is checksummed in parallel.  Once the checksum is
computed, the bio is sent down to the disk, and since we don't control
the order in which the parallel operations happen, they might go down to
the disk in almost any order.

The code deals with this somewhat by having deep work queues for a single
kernel thread, making it very likely that a single thread will process all
the bios for a single inode.

This patch introduces an explicitly ordered work queue.  As work structs
are placed into the queue they are put onto the tail of a list.  They have
three callbacks:

->func (cpu intensive processing here)
->ordered_func (order sensitive processing here)
->ordered_free (free the work struct, all processing is done)

The work struct has three callbacks.  The func callback does the cpu intensive
work, and when it completes the work struct is marked as done.

Every time a work struct completes, the list is checked to see if the head
is marked as done.  If so the ordered_func callback is used to do the
order sensitive processing and the ordered_free callback is used to do
any cleanup.  Then we loop back and check the head of the list again.

This patch also changes the checksumming code to use the ordered workqueues.
One a 4 drive array, it increases streaming writes from 280MB/s to 350MB/s.

Signed-off-by: Chris Mason

Btrfs: fix multi-device code to use raid policies set by mkfs

2008-09-30T23:36:34+00:00

When reading in block groups, a global mask of the available raid policies
should be adjusted based on the types of block groups found on disk.  This
global mask is then used to decide which raid policy to use for new
block groups.

The recent allocator changes dropped the call that updated the global
mask, making all the block groups allocated at run time single striped
onto a single drive.

This also fixes the async worker threads to set any thread that uses
the requeue mechanism as busy.  This allows us to avoid blocking
on get_request_wait for the async bio submission threads.

Signed-off-by: Chris Mason