diff options
Diffstat (limited to 'block/blk-settings.c')
| -rw-r--r-- | block/blk-settings.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/block/blk-settings.c b/block/blk-settings.c index e1327dd..476d870 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -413,10 +413,13 @@ EXPORT_SYMBOL(blk_limits_io_min); * @min: smallest I/O size in bytes * * Description: - * Some devices have an internal block size bigger than the reported - * hardware sector size. This function can be used to signal the - * smallest I/O the device can perform without incurring a performance - * penalty. + * Storage devices may report a granularity or preferred minimum I/O + * size which is the smallest request the device can perform without + * incurring a performance penalty. For disk drives this is often the + * physical block size. For RAID arrays it is often the stripe chunk + * size. A properly aligned multiple of minimum_io_size is the + * preferred request size for workloads where a high number of I/O + * operations is desired. */ void blk_queue_io_min(struct request_queue *q, unsigned int min) { @@ -430,8 +433,12 @@ EXPORT_SYMBOL(blk_queue_io_min); * @opt: optimal request size in bytes * * Description: - * Drivers can call this function to set the preferred I/O request - * size for devices that report such a value. + * Storage devices may report an optimal I/O size, which is the + * device's preferred unit for sustained I/O. This is rarely reported + * for disk drives. For RAID arrays it is usually the stripe width or + * the internal track size. A properly aligned multiple of + * optimal_io_size is the preferred request size for workloads where + * sustained throughput is desired. */ void blk_queue_io_opt(struct request_queue *q, unsigned int opt) { |