Re: scsi optimal_io_size changed from 0 on kernel 6.6, to 16773120(32760*512, 4095*4096) on kernel 6.12/6.16

[Wang Yugui <wangyugui@e16-tech.com>]

Hi,

> scsi optimal_io_size changed
> from 0 on kernel 6.6, 
> to 16773120(32760*512, 4095*4096) on kernel 6.12/6.16
> 
> I tested in on same device and same os dist, but different kernel version.
> both ssd/sas and ssd/sata connected to same hba(mpi3sas driver).
> 
> Is there some feature that changed the default value?

we walked around this problem with a local dirty fix.

diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 351b028ef893..638dbafd695d 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -240,6 +240,9 @@ static int sas_host_setup(struct transport_container *tc, struct device *dev,
 	if (dma_dev->dma_mask) {
 		shost->opt_sectors = min_t(unsigned int, shost->max_sectors,
 				dma_opt_mapping_size(dma_dev) >> SECTOR_SHIFT);
+		/* /sys/block/sda/queue/optimal_io_size 16773120(32760*512, 4095*4096) @T7610 @kernel 6.12+ */
+		shost->opt_sectors = min_t(unsigned int, shost->opt_sectors,
+				SZ_1M >> SECTOR_SHIFT);
 	}
 
 	return 0;

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2025/06/25