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| author | Mike Christie <michael.christie@oracle.com> | 2023-08-17 14:29:02 -0500 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2023-08-21 17:20:48 -0400 |
| commit | 84c073fd89de22d5cb09edffb1f692a1964fd584 (patch) | |
| tree | 747a7abdff001d5a0ff0b65584a2cad5e7193ee2 /drivers/target | |
| parent | 19d7102a953900560811498018bb2de4e27ee9d9 (diff) | |
| download | lwn-84c073fd89de22d5cb09edffb1f692a1964fd584.tar.gz lwn-84c073fd89de22d5cb09edffb1f692a1964fd584.zip | |
scsi: target: Fix write perf due to unneeded throttling
The write back throttling (WBT) code checks if REQ_SYNC | REQ_IDLE is set
to determine if a write is O_DIRECT vs buffered. If the bits are not set
then it assumes it's a buffered write and will throttle LIO if we hit
certain metrics. LIO itself is not using the buffer cache and is doing
direct I/O, so this has us set the direct bits so we are not throttled.
When the initiator application is doing direct I/O this can greatly improve
performance. It depends on the backend device but we have seen where the
WBT code is throttling writes to only 20K IOPs with 4K I/Os when the device
can support 100K+.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230817192902.346791-1-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/target')
| -rw-r--r-- | drivers/target/target_core_iblock.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c index 3d1b511ea284..5937a7ed6989 100644 --- a/drivers/target/target_core_iblock.c +++ b/drivers/target/target_core_iblock.c @@ -740,11 +740,16 @@ iblock_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents, if (data_direction == DMA_TO_DEVICE) { struct iblock_dev *ib_dev = IBLOCK_DEV(dev); + + /* + * Set bits to indicate WRITE_ODIRECT so we are not throttled + * by WBT. + */ + opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; /* * Force writethrough using REQ_FUA if a volatile write cache * is not enabled, or if initiator set the Force Unit Access bit. */ - opf = REQ_OP_WRITE; miter_dir = SG_MITER_TO_SG; if (bdev_fua(ib_dev->ibd_bd)) { if (cmd->se_cmd_flags & SCF_FUA) |