>>>>> "Alan" == Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: Alan> James or Jens, is there a reason why this routine limits Alan> max_sectors to 1024? Alan> And is there a reason why it sets both max_sectors and Alan> max_hw_sectors, leaving no way to change one without the other? The rationale being that we don't want the default value to be too large because it makes I/O choppy on single-spindle setups. If the device driver supports bigger requests we set the hard limit to whatever they support. But filesystem I/O is capped at the default limit which is 1024 for modern devices (and 255 for crappy ones). You can change the current soft limit on a per-device basis in /sys/block/<dev>/queue/max_sectors_kb. I agree it would be nice to have a system-wide default that's not a #define. But given that a lot of queues are created early that's not so easy to do. Alan> Are drivers supposed to assign values directly to Alan> q-> limits.max_sectors? Shouldn't there be a cleaner API for all Alan> this? Drivers are supposed to set the hard limit. The soft limit is a fs/block layer value and none of the device driver's business. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
