From 608128d391fa5c95d515d2c198f40239016e1fcd Mon Sep 17 00:00:00 2001 From: John Garry Date: Thu, 14 Jul 2022 19:15:27 +0800 Subject: scsi: sd: allow max_sectors be capped at DMA optimal size limit Streaming DMA mappings may be considerably slower when mappings go through an IOMMU and the total mapping length is somewhat long. This is because the IOMMU IOVA code allocates and free an IOVA for each mapping, which may affect performance. New member Scsi_Host.opt_sectors is added, which is the optimal host max_sectors, and use this value to cap the request queue max_sectors when set. It could be considered to have request queues io_opt value initially set at Scsi_Host.opt_sectors in __scsi_init_queue(), but that is not really the purpose of io_opt. Finally, even though Scsi_Host.opt_sectors value should never be greater than the request queue max_hw_sectors value, continue to limit to this value for safety. Signed-off-by: John Garry Reviewed-by: Damien Le Moal Acked-by: Martin K. Petersen Signed-off-by: Christoph Hellwig --- drivers/scsi/sd.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/scsi') diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index a1a2ac09066f..3eaee1f7aaca 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -3296,6 +3296,8 @@ static int sd_revalidate_disk(struct gendisk *disk) (sector_t)BLK_DEF_MAX_SECTORS); } + rw_max = min_not_zero(rw_max, sdp->host->opt_sectors); + /* Do not exceed controller limit */ rw_max = min(rw_max, queue_max_hw_sectors(q)); -- cgit v1.2.3-58-ga151