Allow user to set the QUEUE_FLAG_NOWAIT optionally using module
parameter to retain the default behaviour. Also, update respective
allocation flags in the write path. Following are the performance
numbers with io_uring fio engine for random read, note that device has
been populated fully with randwrite workload before taking these
numbers :-
* linux-block (for-next) # grep IOPS pmem*fio | column -t
nowait-off-1.fio: read: IOPS=3968k, BW=15.1GiB/s
nowait-off-2.fio: read: IOPS=4084k, BW=15.6GiB/s
nowait-off-3.fio: read: IOPS=3995k, BW=15.2GiB/s
nowait-on-1.fio: read: IOPS=5909k, BW=22.5GiB/s
nowait-on-2.fio: read: IOPS=5997k, BW=22.9GiB/s
nowait-on-3.fio: read: IOPS=6006k, BW=22.9GiB/s
* linux-block (for-next) # grep cpu pmem*fio | column -t
nowait-off-1.fio: cpu : usr=6.38%, sys=31.37%, ctx=220427659
nowait-off-2.fio: cpu : usr=6.19%, sys=31.45%, ctx=229825635
nowait-off-3.fio: cpu : usr=6.17%, sys=31.22%, ctx=221896158
nowait-on-1.fio: cpu : usr=10.56%, sys=87.82%, ctx=24730
nowait-on-2.fio: cpu : usr=9.92%, sys=88.36%, ctx=23427
nowait-on-3.fio: cpu : usr=9.85%, sys=89.04%, ctx=23237
* linux-block (for-next) # grep slat pmem*fio | column -t
nowait-off-1.fio: slat (nsec): min=431, max=50423k, avg=9424.06
nowait-off-2.fio: slat (nsec): min=420, max=35992k, avg=9193.94
nowait-off-3.fio: slat (nsec): min=430, max=40737k, avg=9244.24
nowait-on-1.fio: slat (nsec): min=1232, max=40098k, avg=7518.60
nowait-on-2.fio: slat (nsec): min=1303, max=52107k, avg=7423.37
nowait-on-3.fio: slat (nsec): min=1123, max=40193k, avg=7409.08
Signed-off-by: Chaitanya Kulkarni <k...@nvidia.com>
---
drivers/nvdimm/pmem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index ceea55f621cc..38defe84de4c 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -31,6 +31,10 @@
#include "pfn.h"
#include "nd.h"
+static bool g_nowait;
+module_param_named(nowait, g_nowait, bool, 0444);
+MODULE_PARM_DESC(nowait, "set QUEUE_FLAG_NOWAIT. Default: False");
+
static struct device *to_dev(struct pmem_device *pmem)
{
/*
@@ -543,6 +547,8 @@ static int pmem_attach_disk(struct device *dev,
blk_queue_max_hw_sectors(q, UINT_MAX);
blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, q);
+ if (g_nowait)
+ blk_queue_flag_set(QUEUE_FLAG_NOWAIT, q);
if (pmem->pfn_flags & PFN_MAP)
blk_queue_flag_set(QUEUE_FLAG_DAX, q);
--
2.40.0
