Commit c807ab520f ("block/mq-deadline: Add I/O priority support")
modified the behavior of request flag BLK_MQ_INSERT_AT_HEAD from
dispatching a request before other requests into dispatching a request
before other requests with the same I/O priority. This is not correct since
BLK_MQ_INSERT_AT_HEAD is used when requeuing requests and also when a flush
request is inserted. Both types of requests should be dispatched as soon
as possible. Hence, make the mq-deadline I/O scheduler again ignore the I/O
priority for BLK_MQ_INSERT_AT_HEAD requests.
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Yu Kuai <yukuai@kernel.org>
Reported-by: chengkaitao <chengkaitao@kylinos.cn>
Closes: https://lore.kernel.org/linux-block/20251009155253.14611-1-pilgrimtao@gmail.com/
Fixes: c807ab520f ("block/mq-deadline: Add I/O priority support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moalv <dlemoal@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Prepare for adding a second caller of this function. No functionality
has been changed.
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Yu Kuai <yukuai@kernel.org>
Cc: chengkaitao <chengkaitao@kylinos.cn>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In commit(fde02699c2), the "if (blk_rq_is_seq_zoned_write(rq))"
was removed, but the "rb_entry_rq(node)" and some other code were
inadvertently left behind. This patch fixed it.
Signed-off-by: chengkaitao <chengkaitao@kylinos.cn>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Li Nan <linan122@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Current depth_updated has some problems:
1) depth_updated() will be called for each hctx, while all elevators
will update async_depth for the disk level, this is not related to hctx;
2) In blk_mq_update_nr_requests(), if previous hctx update succeed and
this hctx update failed, q->nr_requests will not be updated, while
async_depth is already updated with new nr_reqeuests in previous
depth_updated();
3) All elevators are using q->nr_requests to calculate async_depth now,
however, q->nr_requests is still the old value when depth_updated() is
called from blk_mq_update_nr_requests();
Those problems are first from error path, then mq-deadline, and recently
for bfq and kyber, fix those problems by:
- pass in request_queue instead of hctx;
- move depth_updated() after q->nr_requests is updated in
blk_mq_update_nr_requests();
- add depth_updated() call inside init_sched() method to initialize
async_depth;
- remove init_hctx() method for mq-deadline and bfq that is useless now;
Fixes: 77f1e0a52d ("bfq: update internal depth state when queue depth changes")
Fixes: 39823b47bb ("block/mq-deadline: Fix the tag reservation code")
Fixes: 42e6c6ce03 ("lib/sbitmap: convert shallow_depth from one word to the whole sbitmap")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Li Nan <linan122@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250821060612.1729939-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently elevators will record internal 'async_depth' to throttle
asynchronous requests, and they both calculate shallow_dpeth based on
sb->shift, with the respect that sb->shift is the available tags in one
word.
However, sb->shift is not the availbale tags in the last word, see
__map_depth:
if (index == sb->map_nr - 1)
return sb->depth - (index << sb->shift);
For consequence, if the last word is used, more tags can be get than
expected, for example, assume nr_requests=256 and there are four words,
in the worst case if user set nr_requests=32, then the first word is
the last word, and still use bits per word, which is 64, to calculate
async_depth is wrong.
One the ohter hand, due to cgroup qos, bfq can allow only one request
to be allocated, and set shallow_dpeth=1 will still allow the number
of words request to be allocated.
Fix this problems by using shallow_depth to the whole sbitmap instead
of per word, also change kyber, mq-deadline and bfq to follow this,
a new helper __map_depth_with_shallow() is introduced to calculate
available bits in each word.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20250807032413.1469456-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In preparation for allocating sched_tags before freezing the request
queue and acquiring ->elevator_lock, move the elevator queue allocation
logic from the elevator ops ->init_sched callback into blk_mq_init_sched.
As elevator_alloc is now only invoked from block layer core, we don't
need to export it, so unexport elevator_alloc function.
This refactoring provides a centralized location for elevator queue
initialization, which makes it easier to store pre-allocated sched_tags
in the struct elevator_queue during later changes.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250730074614.2537382-2-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_plug_issue_direct(), __blk_mq_flush_plug_list(), and
blk_mq_dispatch_plug_list() take a struct blk_plug * but only use its
mq_list. Pass the struct rq_list * instead in preparation for calling
them with other lists of requests.
Drop "plug" from the function names as they are no longer plug-specific.
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250426011728.4189119-2-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The elevator core now allows instances of 'struct elv_fs_entry' to be
moved into read-only memory. Make use of that to protect them against
accidental or malicious modifications.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20250102-sysfs-const-attr-elevator-v1-2-9837d2058c60@weissschuh.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since commit fde02699c2 ("block: mq-deadline: Remove support for zone
write locking"), the local variable 'insert_before' is assigned once and
is used once. Hence remove this local variable.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20241212212941.1268662-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
req_get_ioprio looks at req->bio to find the I/O priority, which is not
set when completing bios that the driver fully iterated through.
Stash away the dd_per_prio in the elevator private data instead of looking
it up again to optimize the code a bit while fixing the regression from
removing the per-request ioprio value.
Fixes: 6975c1a486 ("block: remove the ioprio field from struct request")
Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Reported-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Tested-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20241126102136.619067-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The current tag reservation code is based on a misunderstanding of the
meaning of data->shallow_depth. Fix the tag reservation code as follows:
* By default, do not reserve any tags for synchronous requests because
for certain use cases reserving tags reduces performance. See also
Harshit Mogalapalli, [bug-report] Performance regression with fio
sequential-write on a multipath setup, 2024-03-07
(https://lore.kernel.org/linux-block/5ce2ae5d-61e2-4ede-ad55-551112602401@oracle.com/)
* Reduce min_shallow_depth to one because min_shallow_depth must be less
than or equal any shallow_depth value.
* Scale dd->async_depth from the range [1, nr_requests] to [1,
bits_per_sbitmap_word].
Cc: Christoph Hellwig <hch@lst.de>
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Zhiguo Niu <zhiguo.niu@unisoc.com>
Fixes: 07757588e5 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240509170149.7639-3-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These functions are defined in the mq-deadline.c file, but not called
elsewhere, so delete these unused functions.
block/mq-deadline.c:134:1: warning: unused function 'deadline_earlier_request'.
block/mq-deadline.c:148:1: warning: unused function 'deadline_latter_request'.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=8803
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240419025610.34298-1-jiapeng.chong@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With the block layer generic plugging of write operations for zoned
block devices, mq-deadline, or any other scheduler, can only ever
see at most one write operation per zone at any time. There is thus no
sequentiality requirements for these writes and thus no need to tightly
control the dispatching of write requests using zone write locking.
Remove all the code that implement this control in the mq-deadline
scheduler and remove advertizing support for the
ELEVATOR_F_ZBD_SEQ_WRITE elevator feature.
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240408014128.205141-22-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The code "max(1U, 3 * (1U << shift) / 4)" comes from the Kyber I/O
scheduler. The Kyber I/O scheduler maintains one internal queue per hwq
and hence derives its async_depth from the number of hwq tags. Using
this approach for the mq-deadline scheduler is wrong since the
mq-deadline scheduler maintains one internal queue for all hwqs
combined. Hence this revert.
Cc: stable@vger.kernel.org
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Cc: Zhiguo Niu <Zhiguo.Niu@unisoc.com>
Fixes: d47f9717e5 ("block/mq-deadline: use correct way to throttling write requests")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240313214218.1736147-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The original formula was inaccurate:
dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
For write requests, when we assign a tags from sched_tags,
data->shallow_depth will be passed to sbitmap_find_bit,
see the following code:
nr = sbitmap_find_bit_in_word(&sb->map[index],
min_t (unsigned int,
__map_depth(sb, index),
depth),
alloc_hint, wrap);
The smaller of data->shallow_depth and __map_depth(sb, index)
will be used as the maximum range when allocating bits.
For a mmc device (one hw queue, deadline I/O scheduler):
q->nr_requests = sched_tags = 128, so according to the previous
calculation method, dd->async_depth = data->shallow_depth = 96,
and the platform is 64bits with 8 cpus, sched_tags.bitmap_tags.sb.shift=5,
sb.maps[]=32/32/32/32, 32 is smaller than 96, whether it is a read or
a write I/O, tags can be allocated to the maximum range each time,
which has not throttling effect.
In addition, refer to the methods of bfg/kyber I/O scheduler,
limit ratiois are calculated base on sched_tags.bitmap_tags.sb.shift.
This patch can throttle write requests really.
Fixes: 07757588e5 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests")
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/1691061162-22898-1-git-send-email-zhiguo.niu@unisoc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A bug was introduced in deadline_from_pos() while implementing the
suggestion to use round_down() in the following code:
pos -= bdev_offset_from_zone_start(rq->q->disk->part0, pos);
This patch makes deadline_from_pos() use round_down() such that 'pos' is
rounded down.
Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/all/5zthzi3lppvcdp4nemum6qck4gpqbdhvgy4k3qwguhgzxc4quj@amulvgycq67h/
Cc: Christoph Hellwig <hch@lst.de>
Cc: Damien Le Moal <dlemoal@kernel.org>
Fixes: 0effb390c4 ("block: mq-deadline: Handle requeued requests correctly")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230712173344.2994513-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Before dispatching a zoned write from the FIFO list, check whether there
are any zoned writes in the RB-tree with a lower LBA for the same zone.
This patch ensures that zoned writes happen in order even if at_head is
set for some writes for a zone and not for others.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230517174230.897144-12-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Start dispatching from the start of a zone instead of from the starting
position of the most recently dispatched request.
If a zoned write is requeued with an LBA that is lower than already
inserted zoned writes, make sure that it is submitted first.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230517174230.897144-11-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Track the position (sector_t) of the most recently dispatched request
instead of tracking a pointer to the next request to dispatch. This
patch is the basis for patch "Handle requeued requests correctly".
Without this patch it would be significantly more complicated to make
sure that zoned writes are dispatched in LBA order per zone.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230517174230.897144-10-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_free_requests() calls dd_finish_request() indirectly. Prevent
nested locking of dd->lock and dd->zone_lock by moving the code for
freeing requests.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230517174230.897144-9-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Make the deadline_skip_seq_writes() code shorter without changing its
functionality.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230517174230.897144-8-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Change the return type of deadline_check_fifo() from 'int' into 'bool'.
Use time_is_before_eq_jiffies() instead of time_after_eq(). No
functionality has been changed.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230517174230.897144-7-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add the missing word "and".
Cc: Damien Le Moal <dlemoal@kernel.org>
Suggested-by: Damien Le Moal <dlemoal@kernel.org>
Fixes: 945ffb60c1 ("mq-deadline: add blk-mq adaptation of the deadline IO scheduler")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230517174230.897144-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of passing a bool at_head, pass down the full flags from the
blk_mq_insert_request interface.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-20-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_sched_insert_request is the main request insert helper and not
directly I/O scheduler related. Move blk_mq_sched_insert_request to
blk-mq.c, rename it to blk_mq_insert_request and mark it static.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_dispatch_plug_list is the only caller of
blk_mq_sched_insert_requests, and it makes sense to just fold it there
as blk_mq_sched_insert_requests isn't specific to I/O schedulers despite
the name.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/blk-mq.h needs various definitions from <linux/blk-mq.h>,
include it there instead of relying on the source files to include
both.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk-mq-tag.h is always included by blk-mq.h, and causes recursive
inclusion hell with further changes. Just merge it into blk-mq.h
instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Rename deadline_is_seq_writes() to deadline_is_seq_write() (remove the
"s" plural) to more correctly reflect the fact that this function tests
a single request, not multiple requests.
Fixes: 015d02f485 ("block: mq-deadline: Do not break sequential write streams to zoned HDDs")
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20221126025550.967914-2-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
mq-deadline ensures an in order dispatching of write requests to zoned
block devices using a per zone lock (a bit). This implies that for any
purely sequential write workload, the drive is exercised most of the
time at a maximum queue depth of one.
However, when such sequential write workload crosses a zone boundary
(when sequentially writing multiple contiguous zones), zone write
locking may prevent the last write to one zone to be issued (as the
previous write is still being executed) but allow the first write to the
following zone to be issued (as that zone is not yet being writen and
not locked). This result in an out of order delivery of the sequential
write commands to the device every time a zone boundary is crossed.
While such behavior does not break the sequential write constraint of
zoned block devices (and does not generate any write error), some zoned
hard-disks react badly to seeing these out of order writes, resulting in
lower write throughput.
This problem can be addressed by always dispatching the first request
of a stream of sequential write requests, regardless of the zones
targeted by these sequential writes. To do so, the function
deadline_skip_seq_writes() is introduced and used in
deadline_next_request() to select the next write command to issue if the
target device is an HDD (blk_queue_nonrot() being false).
deadline_fifo_request() is modified using the new
deadline_earlier_request() and deadline_is_seq_write() helpers to ignore
requests in the fifo list that have a preceding request in lba order
that is sequential.
With this fix, a sequential write workload executed with the following
fio command:
fio --name=seq-write --filename=/dev/sda --zonemode=zbd --direct=1 \
--size=68719476736 --ioengine=libaio --iodepth=32 --rw=write \
--bs=65536
results in an increase from 225 MB/s to 250 MB/s of the write throughput
of an SMR HDD (11% increase).
Cc: <stable@vger.kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20221124021208.242541-3-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
dd_finish_request() tests if the per prio fifo_list is not empty to
determine if request dispatching must be restarted for handling blocked
write requests to zoned devices with a call to
blk_mq_sched_mark_restart_hctx(). While simple, this implementation has
2 problems:
1) Only the priority level of the completed request is considered.
However, writes to a zone may be blocked due to other writes to the
same zone using a different priority level. While this is unlikely to
happen in practice, as writing a zone with different IO priorirites
does not make sense, nothing in the code prevents this from
happening.
2) The use of list_empty() is dangerous as dd_finish_request() does not
take dd->lock and may run concurrently with the insert and dispatch
code.
Fix these 2 problems by testing the write fifo list of all priority
levels using the new helper dd_has_write_work(), and by testing each
fifo list using list_empty_careful().
Fixes: c807ab520f ("block/mq-deadline: Add I/O priority support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20221124021208.242541-2-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the new blk_opf_t type for an argument that represents a bitwise
combination of a request operation and request flags. Rename that
argument from 'op' into 'opf'.
This patch does not change any functionality.
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-9-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
q->elevator is referred in blk_mq_has_sqsched() without any protection,
no .q_usage_counter is held, no queue srcu and rcu read lock is held,
so potential use-after-free may be triggered.
Fix the issue by adding one queue flag for checking if the elevator
uses single queue style dispatch. Meantime the elevator feature flag
of ELEVATOR_F_MQ_AWARE isn't needed any more.
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220616014401.817001-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Before commit 322cff70d4 the fifo_time member of requests on a dispatch
list was not used. Commit 322cff70d4 introduces code that reads the
fifo_time member of requests on dispatch lists. Hence this patch that sets
the fifo_time member when adding a request to a dispatch list.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Fixes: 322cff70d4 ("block/mq-deadline: Prioritize high-priority requests")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220513171307.32564-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A previous commit added this feature, but it inadvertently used the wrong
variable to show/store the setting from/to, victimized by copy/paste. Fix
it up so that the async_depth sysfs interface reads and writes from the
right setting.
Fixes: 07757588e5 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215485
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that we use shared tags for shared sbitmap support, we don't require
the tags sbitmap pointers, so drop them.
This essentially reverts commit 222a5ae03c ("blk-mq: Use pointers for
blk_mq_tags bitmap tags").
Function blk_mq_init_bitmap_tags() is removed also, since it would be only
a wrappper for blk_mq_init_bitmaps().
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1633429419-228500-14-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In addition to reverting commit 7b05bf7710 ("Revert "block/mq-deadline:
Prioritize high-priority requests""), this patch uses 'jiffies' instead
of ktime_get() in the code for aging lower priority requests.
This patch has been tested as follows:
Measured QD=1/jobs=1 IOPS for nullb with the mq-deadline scheduler.
Result without and with this patch: 555 K IOPS.
Measured QD=1/jobs=8 IOPS for nullb with the mq-deadline scheduler.
Result without and with this patch: about 380 K IOPS.
Ran the following script:
set -e
scriptdir=$(dirname "$0")
if [ -e /sys/module/scsi_debug ]; then modprobe -r scsi_debug; fi
modprobe scsi_debug ndelay=1000000 max_queue=16
sd=''
while [ -z "$sd" ]; do
sd=$(basename /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/*)
done
echo $((100*1000)) > "/sys/block/$sd/queue/iosched/prio_aging_expire"
if [ -e /sys/fs/cgroup/io.prio.class ]; then
cd /sys/fs/cgroup
echo restrict-to-be >io.prio.class
echo +io > cgroup.subtree_control
else
cd /sys/fs/cgroup/blkio/
echo restrict-to-be >blkio.prio.class
fi
echo $$ >cgroup.procs
mkdir -p hipri
cd hipri
if [ -e io.prio.class ]; then
echo none-to-rt >io.prio.class
else
echo none-to-rt >blkio.prio.class
fi
{ "${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/low-pri.txt & }
echo $$ >cgroup.procs
"${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/hi-pri.txt
Result:
* 11000 IOPS for the high-priority job
* 40 IOPS for the low-priority job
If the prio aging expiry time is changed from 100s into 0, the IOPS results
change into 6712 and 6796 IOPS.
The max-iops script is a script that runs fio with the following arguments:
--bs=4K --gtod_reduce=1 --ioengine=libaio --ioscheduler=${arg_e} --runtime=60
--norandommap --rw=read --thread --buffered=0 --numjobs=${arg_j}
--iodepth=${arg_d} --iodepth_batch_submit=${arg_a}
--iodepth_batch_complete=$((arg_d / 2)) --name=${positional_argument_1}
--filename=${positional_argument_1}
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20210927220328.1410161-5-bvanassche@acm.org
[axboe: @latest -> @latest_start]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Calculating the sum over all CPUs of per-CPU counters frequently is
inefficient. Hence switch from per-CPU to individual counters. Three
counters are protected by the mq-deadline spinlock since these are
only accessed from contexts that already hold that spinlock. The fourth
counter is atomic because protecting it with the mq-deadline spinlock
would trigger lock contention.
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210927220328.1410161-4-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Check a statistics invariant at module unload time. When running
blktests, the invariant is verified every time a request queue is
removed and hence is verified at least once per test.
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210927220328.1410161-3-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The scheduler .insert_requests() callback is called when a request is
queued for the first time and also when it is requeued. Only count a
request the first time it is queued. Additionally, since the mq-deadline
scheduler only performs zone locking for requests that have been
inserted, skip the zone unlock code for requests that have not been
inserted into the mq-deadline scheduler.
Fixes: 38ba64d12d ("block/mq-deadline: Track I/O statistics")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210927220328.1410161-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Except for the features passed to blk_queue_required_elevator_features,
elevator.h is only needed internally to the block layer. Move the
ELEVATOR_F_* definitions to blkdev.h, and the move elevator.h to
block/, dropping all the spurious includes outside of that.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-13-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If CONFIG_BLK_DEBUG_FS=n:
block/mq-deadline.c:274:12: warning: ‘dd_queued’ defined but not used [-Wunused-function]
274 | static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
| ^~~~~~~~~
Fix this by moving dd_queued() just before the sole function that calls
it.
Fixes: 7b05bf7710 ("Revert "block/mq-deadline: Prioritize high-priority requests"")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: 38ba64d12d ("block/mq-deadline: Track I/O statistics")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210830091128.1854266-1-geert@linux-m68k.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This reverts commit fb926032b3.
Zhen reports that this commit slows down mq-deadline on a 128 thread
box, going from 258K IOPS to 170-180K. My testing shows that Optane
gen2 IOPS goes from 2.3M IOPS to 1.2M IOPS on a 64 thread box.
Looking in detail at the code, the main culprit here is needing to sum
percpu counters in the dispatch hot path, leading to very high CPU
utilization there. To make matters worse, the code currently needs to
sum 2 percpu counters, and it does so in the most naive way of iterating
possible CPUs _twice_.
Since we're close to release, revert this commit and we can re-do it
with regular per-priority counters instead for the 5.15 kernel.
Link: https://lore.kernel.org/linux-block/20210826144039.2143-1-thunder.leizhen@huawei.com/
Reported-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The block layer may call the I/O scheduler .finish_request() callback
without having called the .insert_requests() callback. Make sure that the
mq-deadline I/O statistics are correct if the block layer inserts an I/O
request that bypasses the I/O scheduler. This patch prevents that lower
priority I/O is delayed longer than necessary for mixed I/O priority
workloads.
Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Reported-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Fixes: 08a9ad8bf6 ("block/mq-deadline: Add cgroup support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210824170520.1659173-1-bvanassche@acm.org
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Tested-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This reverts commit 08a9ad8bf6 ("block/mq-deadline: Add cgroup support")
and a follow-up commit c06bc5a3fb ("block/mq-deadline: Remove a
WARN_ON_ONCE() call"). The added cgroup support has the following issues:
* It breaks cgroup interface file format rule by adding custom elements to a
nested key-value file.
* It registers mq-deadline as a cgroup-aware policy even though all it's
doing is collecting per-cgroup stats. Even if we need these stats, this
isn't the right way to add them.
* It hasn't been reviewed from cgroup side.
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Maintain statistics per cgroup and export these to user space. These
statistics are essential for verifying whether the proper I/O priorities
have been assigned to requests. An example of the statistics data with
this patch applied:
$ cat /sys/fs/cgroup/io.stat
11:2 rbytes=0 wbytes=0 rios=3 wios=0 dbytes=0 dios=0 [NONE] dispatched=0 inserted=0 merged=171 [RT] dispatched=0 inserted=0 merged=0 [BE] dispatched=0 inserted=0 merged=0 [IDLE] dispatched=0 inserted=0 merged=0
8:32 rbytes=2142720 wbytes=0 rios=105 wios=0 dbytes=0 dios=0 [NONE] dispatched=0 inserted=0 merged=171 [RT] dispatched=0 inserted=0 merged=0 [BE] dispatched=0 inserted=0 merged=0 [IDLE] dispatched=0 inserted=0 merged=0
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-16-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Track I/O statistics per I/O priority and export these statistics to
debugfs. These statistics help developers of the deadline scheduler.
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-15-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Maintain one dispatch list and one FIFO list per I/O priority class: RT, BE
and IDLE. Maintain statistics for each priority level. Split the debugfs
attributes per priority level as follows:
$ ls /sys/kernel/debug/block/.../sched/
async_depth dispatch2 read_next_rq write2_fifo_list
batching read0_fifo_list starved write_next_rq
dispatch0 read1_fifo_list write0_fifo_list
dispatch1 read2_fifo_list write1_fifo_list
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-14-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When dispatching the first request of a batch, the deadline_move_request()
call clears .next_rq[] for the opposite data direction. .next_rq[] is not
restored when changing data direction. Fix this by not clearing .next_rq[]
and by keeping track of the data direction of a batch in a variable instead.
This patch is a micro-optimization because:
- The number of deadline_next_request() calls for the read direction is
halved.
- The number of times that deadline_next_request() returns NULL is reduced.
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-13-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Bart Van Assche