Block layer currently abuses rq->csd.list.next for storing fifo_time.
That is a terrible hack and completely unnecessary as well. Union
achieves the same space saving in a cleaner way.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
There's a race between elevator switching and normal io operation.
Because the allocation of struct elevator_queue and struct elevator_data
don't in a atomic operation.So there are have chance to use NULL
->elevator_data.
For example:
Thread A: Thread B
blk_queu_bio elevator_switch
spin_lock_irq(q->queue_block) elevator_alloc
elv_merge elevator_init_fn
Because call elevator_alloc, it can't hold queue_lock and the
->elevator_data is NULL.So at the same time, threadA call elv_merge and
nedd some info of elevator_data.So the crash happened.
Move the elevator_alloc into func elevator_init_fn, it make the
operations in a atomic operation.
Using the follow method can easy reproduce this bug
1:dd if=/dev/sdb of=/dev/null
2:while true;do echo noop > scheduler;echo deadline > scheduler;done
The test method also use this method.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Change a timer compare from after to after-equals, thus allowing
0 timeout and making deadline schedule FIFO.
Signed-off-by: xiaobing tu <xiaobing.tu@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
elevator_ops->elevator_init_fn() has a weird return value. It returns
a void * which the caller should assign to q->elevator->elevator_data
and %NULL return denotes init failure.
Update such that it returns integer 0/-errno and sets elevator_data
directly as necessary.
This makes the interface more conventional and eases further cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Let elevators set ->icq_size and ->icq_align in elevator_type and
elv_register() and elv_unregister() respectively create and destroy
kmem_cache for icq.
* elv_register() now can return failure. All callers updated.
* icq caches are automatically named "ELVNAME_io_cq".
* cfq_slab_setup/kill() are collapsed into cfq_init/exit().
* While at it, minor indentation change for iosched_cfq.elevator_name
for consistency.
This will help moving icq management to block core. This doesn't
introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Hi, Jens,
If you recall, I posted an RFC patch for this back in July of last year:
http://lkml.org/lkml/2010/7/13/279
The basic problem is that a process can issue a never-ending stream of
async direct I/Os to the same sector on a device, thus starving out
other I/O in the system (due to the way the alias handling works in both
cfq and deadline). The solution I proposed back then was to start
dispatching from the fifo after a certain number of aliases had been
dispatched. Vivek asked why we had to treat aliases differently at all,
and I never had a good answer. So, I put together a simple patch which
allows aliases to be added to the rb tree (it adds them to the right,
though that doesn't matter as the order isn't guaranteed anyway). I
think this is the preferred solution, as it doesn't break up time slices
in CFQ or batches in deadline. I've tested it, and it does solve the
starvation issue. Let me know what you think.
Cheers,
Jeff
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Deadline currently only batches sector-contiguous requests, so except
for a few circumstances (e.g. requests in a single direction), it is
essentially first come first served. This is bad for throughput, so
change it to CSCAN, which means requests in a batch do not need to be
sequential and are issued in increasing sector order.
Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
elv_register() always returns 0, and there isn't anything it does where
it should return an error (the only error condition is so grave that
it's handled with a BUG_ON).
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
After switching data directions, deadline always starts the next batch
from the lowest-sector request. This gives excessive deadline expiries
and large latency and throughput disparity between high- and low-sector
requests; an order of magnitude in some tests.
This patch changes the batching behaviour so new batches start from the
request whose expiry is earliest.
Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
The deadline I/O scheduler does not reset the batch count when starting
a new batch at a higher-sectored request. This means the second and
subsequent batch in the same data direction will never exceed a single
request in size whenever higher-sectored requests are pending.
This patch gives new batches in the same data direction as old ones
their full quota of requests by resetting the batch count.
Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Factor finding the next request in sector-sorted order into
a function deadline_latter_request.
Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Some of the code has been gradually transitioned to using the proper
struct request_queue, but there's lots left. So do a full sweet of
the kernel and get rid of this typedef and replace its uses with
the proper type.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
kmalloc_node() and kmem_cache_alloc_node() were not available in a zeroing
variant in the past. But with __GFP_ZERO it is possible now to do zeroing
while allocating.
Use __GFP_ZERO to remove the explicit clearing of memory via memset whereever
we can.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- ->init_queue() does not need the elevator passed in
- ->put_request() is a hot path and need not have the queue passed in
- cfq_update_io_seektime() does not need cfqd passed in
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
A big win, we now save an allocation/free on each request! With the
previous rb/hash abstractions, we can just reuse queuelist/donelist
for the FIFO data and be done with it.
Signed-off-by: Jens Axboe <axboe@suse.de>
Right now, every IO scheduler implements its own backmerging (except for
noop, which does no merging). That results in duplicated code for
essentially the same operation, which is never a good thing. This patch
moves the backmerging out of the io schedulers and into the elevator
core. We save 1.6kb of text and as a bonus get backmerging for noop as
well. Win-win!
Signed-off-by: Jens Axboe <axboe@suse.de>
Jan Kara
Joe Perches
Jianpeng Ma
Kent Overstreet
xiaobing tu
Tejun Heo
Jeff Moyer
Jens Axboe
Jens Axboe
Aaron Carroll
Adrian Bunk
Christoph Lameter
Jens Axboe
Jens Axboe
Jörn Engel