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scsi: target: Allow userspace to request direct submissions

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This allows userspace to request the fabric drivers do direct submissions
if they support it. With the new device file, submit_type, users can
write 0 - 2 to control how commands are submitted to the backend:

 0 - TARGET_FABRIC_DEFAULT_SUBMIT - LIO will use the fabric's default
     submission type. This is the default for compat.

 1 - TARGET_DIRECT_SUBMIT - LIO will submit the cmd to the backend from the
     calling context if the fabric the cmd was received on supports it,
     else it will use the fabric's default type.

 2 - TARGET_QUEUE_SUBMIT - LIO will queue the cmd to the LIO submission
     workqueue which will pass it to the backend.

When using an NVMe drive and vhost-scsi with direct submission we see
around a 20% improvement in 4K I/Os:

fio jobs        1       2       4       8       10
--------------------------------------------------
defer           94K     190K    394K    770K    890K
direct          128K    252K    488K    950K    -

And when using the queueing mode, we now no longer see issues like where
the iSCSI tx thread is blocked in the block layer waiting on a tag so it
can't respond to a nop or perform I/Os for other LUs.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-6-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mike Christie
2023-09-27 21:09:05 -05:00
committed by Martin K. Petersen
parent 428926796e
commit e2f4ea4013
6 changed files with 57 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/target/target_core_configfs.c
+22
View File
@@ -577,6 +577,7 @@ DEF_CONFIGFS_ATTRIB_SHOW(unmap_granularity_alignment);
DEF_CONFIGFS_ATTRIB_SHOW(unmap_zeroes_data);
DEF_CONFIGFS_ATTRIB_SHOW(max_write_same_len);
DEF_CONFIGFS_ATTRIB_SHOW(emulate_rsoc);
DEF_CONFIGFS_ATTRIB_SHOW(submit_type);
#define DEF_CONFIGFS_ATTRIB_STORE_U32(_name) \
static ssize_t _name##_store(struct config_item *item, const char *page,\
@@ -1231,6 +1232,24 @@ static ssize_t emulate_rsoc_store(struct config_item *item,
return count;
}
static ssize_t submit_type_store(struct config_item *item, const char *page,
size_t count)
{
struct se_dev_attrib *da = to_attrib(item);
int ret;
u8 val;
ret = kstrtou8(page, 0, &val);
if (ret < 0)
return ret;
if (val > TARGET_QUEUE_SUBMIT)
return -EINVAL;
da->submit_type = val;
return count;
}
CONFIGFS_ATTR(, emulate_model_alias);
CONFIGFS_ATTR(, emulate_dpo);
CONFIGFS_ATTR(, emulate_fua_write);
@@ -1266,6 +1285,7 @@ CONFIGFS_ATTR(, unmap_zeroes_data);
CONFIGFS_ATTR(, max_write_same_len);
CONFIGFS_ATTR(, alua_support);
CONFIGFS_ATTR(, pgr_support);
CONFIGFS_ATTR(, submit_type);
/*
* dev_attrib attributes for devices using the target core SBC/SPC
@@ -1308,6 +1328,7 @@ struct configfs_attribute *sbc_attrib_attrs[] = {
&attr_alua_support,
&attr_pgr_support,
&attr_emulate_rsoc,
&attr_submit_type,
NULL,
};
EXPORT_SYMBOL(sbc_attrib_attrs);
@@ -1325,6 +1346,7 @@ struct configfs_attribute *passthrough_attrib_attrs[] = {
&attr_emulate_pr,
&attr_alua_support,
&attr_pgr_support,
&attr_submit_type,
NULL,
};
EXPORT_SYMBOL(passthrough_attrib_attrs);