From 84c073fd89de22d5cb09edffb1f692a1964fd584 Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Thu, 17 Aug 2023 14:29:02 -0500 Subject: [PATCH] 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 Link: https://lore.kernel.org/r/20230817192902.346791-1-michael.christie@oracle.com Signed-off-by: Martin K. Petersen --- drivers/target/target_core_iblock.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) 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) -- 2.25.1