@@ -3686,6 +3686,32 @@ static void sd_read_block_zero(struct scsi_disk *sdkp)
kfree(buffer);
}
+/*
+ * Set the optimal I/O size: limit the default to the SCSI host optimal sector
+ * limit if it is set. There may be an impact on performance when the size of
+ * a request exceeds this host limit. If the host did not set any optimal
+ * sector limit and the device did not indicate an optimal transfer size
+ * (e.g. ATA devices), default to using the device max_sectors limit.
+ */
+static void sd_set_io_opt(struct scsi_disk *sdkp, unsigned int dev_max,
+ struct queue_limits *lim)
+{
+ struct scsi_device *sdp = sdkp->device;
+ struct Scsi_Host *shost = sdp->host;
+
+ lim->io_opt = shost->opt_sectors << SECTOR_SHIFT;
+ if (sd_validate_opt_xfer_size(sdkp, dev_max))
+ lim->io_opt = min_not_zero(lim->io_opt,
+ logical_to_bytes(sdp, sdkp->opt_xfer_blocks));
+ if (!lim->io_opt) {
+ lim->io_opt = ALIGN_DOWN(lim->max_sectors << SECTOR_SHIFT,
+ sdkp->physical_block_size - 1);
+ sd_first_printk(KERN_WARNING, sdkp,
+ "Using default optimal transfer size of %u bytes\n",
+ lim->io_opt);
+ }
+}
+
/**
* sd_revalidate_disk - called the first time a new disk is seen,
* performs disk spin up, read_capacity, etc.
@@ -3782,16 +3808,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
else
lim.io_min = 0;
- /*
- * Limit default to SCSI host optimal sector limit if set. There may be
- * an impact on performance for when the size of a request exceeds this
- * host limit.
- */
- lim.io_opt = sdp->host->opt_sectors << SECTOR_SHIFT;
- if (sd_validate_opt_xfer_size(sdkp, dev_max)) {
- lim.io_opt = min_not_zero(lim.io_opt,
- logical_to_bytes(sdp, sdkp->opt_xfer_blocks));
- }
+ sd_set_io_opt(sdkp, dev_max, &lim);
sdkp->first_scan = 0;
Introduce the helper function sd_set_io_opt() to set a disk io_opt limit. This new way of setting this limit falls back to using the max_sectors limit if the host does not define an optimal sector limit and the device did not indicate an optimal transfer size (e.g. as is the case for ATA devices). This fallback io_opt limit avoids the disk to be setup with the rather small 128 KB for as the read_ahead_kb attribute. The larger read_ahead_kb value set with the default io_opt limit significantly improves buffered read performance with file systems without any intervention from the user. Signed-off-by: Damien Le Moal <dlemoal@kernel.org> --- drivers/scsi/sd.c | 37 +++++++++++++++++++++++++++---------- 1 file changed, 27 insertions(+), 10 deletions(-)