Commit 88755bda authored by Ming Lei's avatar Ming Lei Committed by Zheng Qixing
Browse files

scsi: core: Replace sdev->device_busy with sbitmap 

mainline inclusion
from mainline-v5.13-rc1
commit 020b0f0a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/IB4C27

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=020b0f0a31920e5b7e7e120d4560453b67b70733

-------------------------------------------

SCSI currently uses an atomic variable to track queue depth for each
attached device. The queue depth depends on many factors such as transport
type and device implementation. In addition, the SCSI device queue depth is
not a static entity but changes over time as a result of congestion
management.

While blk-mq currently tracks queue depth for each hctx, it can't easily be
changed to accommodate the SCSI per-device requirement.

The current approach of using an atomic variable doesn't scale well when
there are lots of CPU cores and the disk is very fast. IOPS can be
substantially impacted by the atomic in the hot path.

Replace the atomic variable sdev->device_busy with an sbitmap for tracking
the SCSI device queue depth.

It has been observed that IOPS is improved ~30% by this patchset in the
following test:

1) test machine(32 logical CPU cores)
	Thread(s) per core:  2
	Core(s) per socket:  8
	Socket(s):           2
	NUMA node(s):        2
	Model name:          Intel(R) Xeon(R) Silver 4110 CPU @ 2.10GHz

2) setup scsi_debug:
modprobe scsi_debug virtual_gb=128 max_luns=1 submit_queues=32 delay=0 max_queue=256

3) fio script:
fio --rw=randread --size=128G --direct=1 --ioengine=libaio --iodepth=2048 \
	--numjobs=32 --bs=4k --group_reporting=1 --group_reporting=1 --runtime=60 \
	--loops=10000 --name=job1 --filename=/dev/sdN

[mkp: fix device_busy reference in mpt3sas]

Link: https://lore.kernel.org/r/20210122023317.687987-14-ming.lei@redhat.com
Link: https://lore.kernel.org/linux-block/20200119071432.18558-6-ming.lei@redhat.com/


Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: default avatarSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>

Conflicts:
	drivers/scsi/mpt3sas/mpt3sas_base.c
[The conflict here is due to the lack of introduction of commit
664f0dce ("scsi: mpt3sas: Add support for shared host tagset
for CPU hotplug").]
Signed-off-by: default avatarZheng Qixing <zhengqixing@huawei.com>
parent 73a66572

drivers/scsi/scsi.c

+3 −1
Original line number Diff line number Diff line
@@ -218,7 +218,7 @@ void scsi_finish_command(struct scsi_cmnd *cmd) 
/*

 * 1024 is big enough for saturating the fast scsi LUN now

 */

static int scsi_device_max_queue_depth(struct scsi_device *sdev)

int scsi_device_max_queue_depth(struct scsi_device *sdev)

{

	return max_t(int, sdev->host->can_queue, 1024);

}
@@ -242,6 +242,8 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth) 
	if (sdev->request_queue)

		blk_set_queue_depth(sdev->request_queue, depth);



	sbitmap_resize(&sdev->budget_map, sdev->queue_depth);



	return sdev->queue_depth;

}

EXPORT_SYMBOL(scsi_change_queue_depth);

drivers/scsi/scsi_lib.c

+18 −17
Original line number Diff line number Diff line
@@ -333,7 +333,7 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd) 
	if (starget->can_queue > 0)

		atomic_dec(&starget->target_busy);



	atomic_dec(&sdev->device_busy);

	sbitmap_put(&sdev->budget_map, cmd->budget_token);

	cmd->budget_token = -1;

}
@@ -1258,19 +1258,20 @@ scsi_device_state_check(struct scsi_device *sdev, struct request *req) 
}



/*

 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else

 * return 0.

 *

 * Called with the queue_lock held.

 * scsi_dev_queue_ready: if we can send requests to sdev, assign one token

 * and return the token else return -1.

 */

static inline int scsi_dev_queue_ready(struct request_queue *q,

				  struct scsi_device *sdev)

{

	unsigned int busy;

	int token;



	busy = atomic_inc_return(&sdev->device_busy) - 1;

	token = sbitmap_get(&sdev->budget_map);

	if (atomic_read(&sdev->device_blocked)) {

		if (busy)

		if (token < 0)

			goto out;



		if (scsi_device_busy(sdev) > 1)

			goto out_dec;



		/*
@@ -1282,13 +1283,12 @@ static inline int scsi_dev_queue_ready(struct request_queue *q, 
				   "unblocking device at zero depth\n"));

	}



	if (busy >= sdev->queue_depth)

		goto out_dec;



	return 1;

	return token;

out_dec:

	atomic_dec(&sdev->device_busy);

	return 0;

	if (token >= 0)

		sbitmap_put(&sdev->budget_map, token);

out:

	return -1;

}



/*
@@ -1615,15 +1615,16 @@ static void scsi_mq_put_budget(struct request_queue *q, int budget_token) 
{

	struct scsi_device *sdev = q->queuedata;



	atomic_dec(&sdev->device_busy);

	sbitmap_put(&sdev->budget_map, budget_token);

}



static int scsi_mq_get_budget(struct request_queue *q)

{

	struct scsi_device *sdev = q->queuedata;

	int token = scsi_dev_queue_ready(q, sdev);



	if (scsi_dev_queue_ready(q, sdev))

		return 0;

	if (token >= 0)

		return token;



	atomic_inc(&sdev->restarts);

drivers/scsi/scsi_priv.h

+3 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
#include <linux/device.h>

#include <linux/async.h>

#include <scsi/scsi_device.h>

#include <linux/sbitmap.h>



struct request_queue;

struct request;
@@ -182,6 +183,8 @@ static inline void scsi_dh_add_device(struct scsi_device *sdev) { } 
static inline void scsi_dh_release_device(struct scsi_device *sdev) { }

#endif



extern int scsi_device_max_queue_depth(struct scsi_device *sdev);



/* 

 * internal scsi timeout functions: for use by mid-layer and transport

 * classes.

drivers/scsi/scsi_scan.c

+21 −2
Original line number Diff line number Diff line
@@ -215,6 +215,7 @@ static void scsi_unlock_floptical(struct scsi_device *sdev, 
static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,

					   u64 lun, void *hostdata)

{

	unsigned int depth;

	struct scsi_device *sdev;

	int display_failure_msg = 1, ret;

	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
@@ -276,8 +277,25 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget, 
	WARN_ON_ONCE(!blk_get_queue(sdev->request_queue));

	sdev->request_queue->queuedata = sdev;



	scsi_change_queue_depth(sdev, sdev->host->cmd_per_lun ?

					sdev->host->cmd_per_lun : 1);

	depth = sdev->host->cmd_per_lun ?: 1;



	/*

	 * Use .can_queue as budget map's depth because we have to

	 * support adjusting queue depth from sysfs. Meantime use

	 * default device queue depth to figure out sbitmap shift

	 * since we use this queue depth most of times.

	 */

	if (sbitmap_init_node(&sdev->budget_map,

				scsi_device_max_queue_depth(sdev),

				sbitmap_calculate_shift(depth),

				GFP_KERNEL, sdev->request_queue->node,

				false, true)) {

		put_device(&starget->dev);

		kfree(sdev);

		goto out;

	}



	scsi_change_queue_depth(sdev, depth);



	scsi_sysfs_device_initialize(sdev);
@@ -980,6 +998,7 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result, 
		scsi_attach_vpd(sdev);



	sdev->max_queue_depth = sdev->queue_depth;

	WARN_ON_ONCE(sdev->max_queue_depth > sdev->budget_map.depth);

	sdev->sdev_bflags = *bflags;



	/*

drivers/scsi/scsi_sysfs.c

+2 −0
Original line number Diff line number Diff line
@@ -480,6 +480,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) 
	/* NULL queue means the device can't be used */

	sdev->request_queue = NULL;



	sbitmap_free(&sdev->budget_map);



	mutex_lock(&sdev->inquiry_mutex);

	vpd_pg0 = rcu_replace_pointer(sdev->vpd_pg0, vpd_pg0,

				       lockdep_is_held(&sdev->inquiry_mutex));