LIO wants to complete a cmd on the CPU it was submitted on, because
most drivers have per cpu or hw queue handlers. But, for vhost-scsi
which has the single thread for submissions and completions this
is not always the best thing to do since the thread could be running
on a different CPU now, and it conflicts with what the user has setup
in the lower levels with settings like the block layer rq_affinity
or for network block devices what the user has setup on their nic.
This patch has vhost-scsi tell LIO to complete the cmd on the CPU the
layer below LIO has completed the cmd on. We then stop fighting
the block, net and whatever layer/setting is below us.
With this patch and the previous ones I see an increase in IOPs by about
50% (234K -> 350K) for random 4K workloads like:
fio --filename=/dev/sda --direct=1 --rw=randrw --bs=4k
--ioengine=libaio --iodepth=128 --numjobs=8 --time_based
--group_reporting --runtime=60
Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/target/target_core_transport.c | 10 +++++++++-
drivers/vhost/scsi.c | 3 ++-
include/target/target_core_base.h | 2 ++
3 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index b1f920c1b816..e5e555dcd73a 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -828,7 +828,12 @@ static void target_queue_cmd_work(struct se_cmd_queue *q, struct se_cmd *se_cmd,
static void target_queue_cmd_compl(struct se_cmd *se_cmd)
{
struct se_device *se_dev = se_cmd->se_dev;
- int cpu = se_cmd->cpuid;
+ int cpu;
+
+ if (se_cmd->se_cmd_flags & SCF_IGNORE_CPUID_COMPL)
+ cpu = smp_processor_id();
+ else
+ cpu = se_cmd->cpuid;
target_queue_cmd_work(&se_dev->queues[cpu].cq, se_cmd, cpu,
target_completion_wq);
@@ -1609,6 +1614,9 @@ target_submit_prep(struct se_cmd *se_cmd, struct se_session *se_sess,
BUG_ON(!se_tpg);
BUG_ON(se_cmd->se_tfo || se_cmd->se_sess);
+ if (flags & TARGET_SCF_IGNORE_CPUID_COMPL)
+ se_cmd->se_cmd_flags |= SCF_IGNORE_CPUID_COMPL;
+
if (flags & TARGET_SCF_USE_CPUID)
se_cmd->se_cmd_flags |= SCF_USE_CPUID;
/*
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 99909c6f3960..b9addd5fdd28 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -803,7 +803,8 @@ static void vhost_scsi_target_queue_cmd(struct vhost_scsi_cmd *cmd)
&cmd->tvc_sense_buf[0], cmd->tvc_lun,
cmd->tvc_exp_data_len,
vhost_scsi_to_tcm_attr(cmd->tvc_task_attr),
- cmd->tvc_data_direction, TARGET_SCF_ACK_KREF,
+ cmd->tvc_data_direction,
+ TARGET_SCF_ACK_KREF | TARGET_SCF_IGNORE_CPUID_COMPL,
sg_ptr, cmd->tvc_sgl_count, NULL, 0, sg_prot_ptr,
cmd->tvc_prot_sgl_count);
if (rc < 0) {
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index f2ba7de59da7..bb4ac7e6f560 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -146,6 +146,7 @@ enum se_cmd_flags_table {
SCF_USE_CPUID = (1 << 16),
SCF_TASK_ATTR_SET = (1 << 17),
SCF_TREAT_READ_AS_NORMAL = (1 << 18),
+ SCF_IGNORE_CPUID_COMPL = (1 << 19)
};
/*
@@ -195,6 +196,7 @@ enum target_sc_flags_table {
TARGET_SCF_ACK_KREF = 0x02,
TARGET_SCF_UNKNOWN_SIZE = 0x04,
TARGET_SCF_USE_CPUID = 0x08,
+ TARGET_SCF_IGNORE_CPUID_COMPL = 0x10,
};
/* fabric independent task management function values */
--
2.25.1
