QUEUE_FLAG_NOWAIT is set by default to mq drivers such null_blk when
it is used with NULL_Q_MQ mode as a part of QUEUE_FLAG_MQ_DEFAULT that
gets assigned in following code path see blk_mq_init_allocated_queue():-
null_add_dev()
if (dev->queue_mode == NULL_Q_MQ) {
blk_mq_alloc_disk()
__blk_mq_alloc_disk()
blk_mq_init_queue_data()
blk_mq_init_allocated_queue()
q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
}
But it is not set when null_blk is loaded with NULL_Q_BIO mode in following
code path like other bio drivers do e.g. nvme-multipath :-
if (dev->queue_mode == NULL_Q_BIO) {
nullb->disk = blk_alloc_disk(nullb->dev->home_node);
blk_alloc_disk()
blk_alloc_queue()
__alloc_disk_nodw()
}
Add a new module parameter nowait and respective configfs attr that will
set or clear the QUEUE_FLAG_NOWAIT based on a value set by user in
null_add_dev() irrespective of the queue mode, by default keep it
enabled to retain the original behaviour for the NULL_Q_MQ mode.
Depending on nowait value use GFP_NOWAIT or GFP_NOIO for the alloction
in the null_alloc_page() for alloc_pages() and in null_insert_page()
for radix_tree_preload().
Observed performance difference with this patch for fio iouring with
configfs and non configfs null_blk with queue modes NULL_Q_BIO and
NULL_Q_MQ:-
* Configfs Membacked mode:-
NULL_Q_BIO mode QUEUE_FLAG_NOWAIT disabled :-
---------------------------------------------
configfs-qmode-0-nowait-0-fio-1.log: read: IOPS=1295k, BW=5058MiB/s
configfs-qmode-0-nowait-0-fio-2.log: read: IOPS=1362k, BW=5318MiB/s
configfs-qmode-0-nowait-0-fio-3.log: read: IOPS=1332k, BW=5201MiB/s
NULL_Q_BIO mode QUEUE_FLAG_NOWAIT enabled :-
---------------------------------------------
configfs-qmode-0-nowait-1-fio-1.log: read: IOPS=2095k, BW=8183MiB/s
configfs-qmode-0-nowait-1-fio-2.log: read: IOPS=2085k, BW=8145MiB/s
configfs-qmode-0-nowait-1-fio-3.log: read: IOPS=2036k, BW=7955MiB/s
NULL_Q_MQ mode QUEUE_FLAG_NOWAIT disabled :-
---------------------------------------------
configfs-qmode-2-nowait-0-fio-1.log: read: IOPS=1288k, BW=5031MiB/s
configfs-qmode-2-nowait-0-fio-2.log: read: IOPS=1239k, BW=4839MiB/s
configfs-qmode-2-nowait-0-fio-3.log: read: IOPS=1252k, BW=4889MiB/s
NULL_Q_MQ mode QUEUE_FLAG_NOWAIT enabled :-
---------------------------------------------
configfs-qmode-2-nowait-1-fio-1.log: read: IOPS=2101k, BW=8208MiB/s
configfs-qmode-2-nowait-1-fio-2.log: read: IOPS=2091k, BW=8169MiB/s
configfs-qmode-2-nowait-1-fio-3.log: read: IOPS=2088k, BW=8155MiB/s
* Non Configfs non-membacked mode:-
NULL_Q_BIO mode QUEUE_FLAG_NOWAIT disabled :-
---------------------------------------------
qmode-0-nowait-0-fio-1.log: read: IOPS=1362k, BW=5321MiB/s
qmode-0-nowait-0-fio-2.log: read: IOPS=1334k, BW=5210MiB/s
qmode-0-nowait-0-fio-3.log: read: IOPS=1386k, BW=5416MiB/s
NULL_Q_BIO mode QUEUE_FLAG_NOWAIT enabled :-
---------------------------------------------
qmode-0-nowait-1-fio-1.log: read: IOPS=5405k, BW=20.6GiB/s
qmode-0-nowait-1-fio-2.log: read: IOPS=5502k, BW=21.0GiB/s
qmode-0-nowait-1-fio-3.log: read: IOPS=5518k, BW=21.0GiB/s
NULL_Q_MQ mode QUEUE_FLAG_NOWAIT disabled :-
---------------------------------------------
qmode-2-nowait-0-fio-1.log: read: IOPS=1356k, BW=5296MiB/s
qmode-2-nowait-0-fio-2.log: read: IOPS=1318k, BW=5148MiB/s
qmode-2-nowait-0-fio-3.log: read: IOPS=1252k, BW=4891MiB/s
NULL_Q_MQ mode QUEUE_FLAG_NOWAIT enabled :-
---------------------------------------------
qmode-2-nowait-1-fio-1.log: read: IOPS=5466k, BW=20.9GiB/s
qmode-2-nowait-1-fio-2.log: read: IOPS=5446k, BW=20.8GiB/s
qmode-2-nowait-1-fio-3.log: read: IOPS=5482k, BW=20.9GiB/s
Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
---
In caes prep patch is needed (ideally it should be) for adding
gfp args to null_alloc_page() please let me know.
-ck
drivers/block/null_blk/main.c | 22 +++++++++++++++++-----
drivers/block/null_blk/null_blk.h | 1 +
2 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index bc2c58724df3..67683f2fd6e1 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -77,6 +77,10 @@ enum {
NULL_IRQ_TIMER = 2,
};
+static bool g_nowait = true;
+module_param_named(nowait, g_nowait, bool, 0444);
+MODULE_PARM_DESC(virt_boundary, "Set QUEUE_FLAG_NOWAIT irrespective of queue mode. Default: True");
+
static bool g_virt_boundary = false;
module_param_named(virt_boundary, g_virt_boundary, bool, 0444);
MODULE_PARM_DESC(virt_boundary, "Require a virtual boundary for the device. Default: False");
@@ -413,6 +417,7 @@ NULLB_DEVICE_ATTR(irqmode, uint, NULL);
NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL);
NULLB_DEVICE_ATTR(index, uint, NULL);
NULLB_DEVICE_ATTR(blocking, bool, NULL);
+NULLB_DEVICE_ATTR(nowait, bool, NULL);
NULLB_DEVICE_ATTR(use_per_node_hctx, bool, NULL);
NULLB_DEVICE_ATTR(memory_backed, bool, NULL);
NULLB_DEVICE_ATTR(discard, bool, NULL);
@@ -554,6 +559,7 @@ static struct configfs_attribute *nullb_device_attrs[] = {
&nullb_device_attr_hw_queue_depth,
&nullb_device_attr_index,
&nullb_device_attr_blocking,
+ &nullb_device_attr_nowait,
&nullb_device_attr_use_per_node_hctx,
&nullb_device_attr_power,
&nullb_device_attr_memory_backed,
@@ -628,7 +634,7 @@ nullb_group_drop_item(struct config_group *group, struct config_item *item)
static ssize_t memb_group_features_show(struct config_item *item, char *page)
{
return snprintf(page, PAGE_SIZE,
- "badblocks,blocking,blocksize,cache_size,"
+ "badblocks,blocking,nowait,blocksize,cache_size,"
"completion_nsec,discard,home_node,hw_queue_depth,"
"irqmode,max_sectors,mbps,memory_backed,no_sched,"
"poll_queues,power,queue_mode,shared_tag_bitmap,size,"
@@ -696,6 +702,7 @@ static struct nullb_device *null_alloc_dev(void)
dev->irqmode = g_irqmode;
dev->hw_queue_depth = g_hw_queue_depth;
dev->blocking = g_blocking;
+ dev->nowait = g_nowait;
dev->memory_backed = g_memory_backed;
dev->discard = g_discard;
dev->cache_size = g_cache_size;
@@ -830,7 +837,7 @@ static void null_complete_rq(struct request *rq)
end_cmd(blk_mq_rq_to_pdu(rq));
}
-static struct nullb_page *null_alloc_page(void)
+static struct nullb_page *null_alloc_page(gfp_t gfp)
{
struct nullb_page *t_page;
@@ -838,7 +845,7 @@ static struct nullb_page *null_alloc_page(void)
if (!t_page)
return NULL;
- t_page->page = alloc_pages(GFP_NOIO, 0);
+ t_page->page = alloc_pages(gfp, 0);
if (!t_page->page) {
kfree(t_page);
return NULL;
@@ -983,11 +990,11 @@ static struct nullb_page *null_insert_page(struct nullb *nullb,
spin_unlock_irq(&nullb->lock);
- t_page = null_alloc_page();
+ t_page = null_alloc_page(nullb->dev->nowait ? GFP_NOWAIT : GFP_NOIO);
if (!t_page)
goto out_lock;
- if (radix_tree_preload(GFP_NOIO))
+ if (radix_tree_preload(nullb->dev->nowait ? GFP_NOWAIT : GFP_NOIO))
goto out_freepage;
spin_lock_irq(&nullb->lock);
@@ -2093,6 +2100,11 @@ static int null_add_dev(struct nullb_device *dev)
blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);
+ if (dev->nowait)
+ blk_queue_flag_set(QUEUE_FLAG_NOWAIT, nullb->q);
+ else
+ blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, nullb->q);
+
mutex_lock(&lock);
rv = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL);
if (rv < 0) {
diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index eb5972c50be8..1d7af446d728 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -107,6 +107,7 @@ struct nullb_device {
unsigned int index; /* index of the disk, only valid with a disk */
unsigned int mbps; /* Bandwidth throttle cap (in MB/s) */
bool blocking; /* blocking blk-mq device */
+ bool nowait; /* to set QUEUE_FLAG_NOWAIT on device queue */
bool use_per_node_hctx; /* use per-node allocation for hardware context */
bool power; /* power on/off the device */
bool memory_backed; /* if data is stored in memory */
--
2.29.0
