From 4cbfca5f7750520ff993a0d6eb79cc4a6f6cee97 Mon Sep 17 00:00:00 2001 From: John Garry Date: Thu, 14 Jul 2022 19:15:28 +0800 Subject: scsi: scsi_transport_sas: cap shost opt_sectors according to DMA optimal 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. For performance reasons set the request queue max_sectors from dma_opt_mapping_size(), which knows this mapping limit. Signed-off-by: John Garry Reviewed-by: Damien Le Moal Signed-off-by: Christoph Hellwig --- drivers/scsi/scsi_transport_sas.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c index 12bff64dade6..2f88c61216ee 100644 --- a/drivers/scsi/scsi_transport_sas.c +++ b/drivers/scsi/scsi_transport_sas.c @@ -225,6 +225,7 @@ static int sas_host_setup(struct transport_container *tc, struct device *dev, { struct Scsi_Host *shost = dev_to_shost(dev); struct sas_host_attrs *sas_host = to_sas_host_attrs(shost); + struct device *dma_dev = shost->dma_dev; INIT_LIST_HEAD(&sas_host->rphy_list); mutex_init(&sas_host->lock); @@ -236,6 +237,11 @@ static int sas_host_setup(struct transport_container *tc, struct device *dev, dev_printk(KERN_ERR, dev, "fail to a bsg device %d\n", shost->host_no); + if (dma_dev->dma_mask) { + shost->opt_sectors = min_t(unsigned int, shost->max_sectors, + dma_opt_mapping_size(dma_dev) >> SECTOR_SHIFT); + } + return 0; } -- cgit