diff options
| author | Andrei Vagin <avagin@openvz.org> | 2018-03-21 23:55:02 -0700 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2018-05-14 22:40:08 -0400 |
| commit | 769031c92c8b85bd886f7e064430b7b512c68728 (patch) | |
| tree | aeb339bce1641974aba11403c6bdd702c6ea119b /drivers/target/target_core_file.h | |
| parent | 97e066184b855dd2df4e82c2d1feff37282c53fd (diff) | |
scsi: target: target/file: Add support of direct and async I/O
There are two advantages:
* Direct I/O allows to avoid the write-back cache, so it reduces affects
to other processes in the system.
* Async I/O allows to handle a few commands concurrently.
DIO + AIO shows a better perfomance for random write operations:
Mode: O_DSYNC Async: 1
$ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sda --runtime=20 --numjobs=2
WRITE: bw=45.9MiB/s (48.1MB/s), 21.9MiB/s-23.0MiB/s (22.0MB/s-25.2MB/s), io=919MiB (963MB), run=20002-20020msec
Mode: O_DSYNC Async: 0
$ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sdb --runtime=20 --numjobs=2
WRITE: bw=1607KiB/s (1645kB/s), 802KiB/s-805KiB/s (821kB/s-824kB/s), io=31.8MiB (33.4MB), run=20280-20295msec
Known issue:
DIF (PI) emulation doesn't work when a target uses async I/O, because
DIF metadata is saved in a separate file, and it is another non-trivial
task how to synchronize writing in two files, so that a following read
operation always returns a consisten metadata for a specified block.
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Tested-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/target/target_core_file.h')
| -rw-r--r-- | drivers/target/target_core_file.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/target/target_core_file.h b/drivers/target/target_core_file.h index 53be5ffd3261..929b1ecd544e 100644 --- a/drivers/target/target_core_file.h +++ b/drivers/target/target_core_file.h @@ -22,6 +22,7 @@ #define FBDF_HAS_PATH 0x01 #define FBDF_HAS_SIZE 0x02 #define FDBD_HAS_BUFFERED_IO_WCE 0x04 +#define FDBD_HAS_ASYNC_IO 0x08 #define FDBD_FORMAT_UNIT_SIZE 2048 struct fd_dev { |