Please don't drop the cc list ... part of the point of this is to create an archive record for people with similar questions to find. On Sat, 2009-06-20 at 20:11 +0530, Ravish Tayal wrote: > Thanks James. > > For simple case when I echo few lines to usb mounted disk (fat file > system). > > mkdir /var/disk1 > mount /dev/sda /var/disk1 > echo "TESTing " >/var/disk1/test.txt > > in this case will it be echo commands context it will be queue the > commands to scsiglue.c or in between scsi layer would hold the > commands. That echo will end up in the page cache as a dirty page. > I have noticed on usb analyser the write scsi commands happens for max > sector size (64K) ... does in this case scsi command would be happen > for few bytes ? Block commands all have to happen at a granularity of the device block size (512b usually). The elevators try to build up to larger sizes. > or in other words is pdflush invokation indirectly control the WRITE > scsi command length if file is of few MB or scsi layer itself does > ot ? The elevators control final request size depending on what inputs they have and what parameters they were given. In all cases, the request will be a multiple of the filesystem block size (which will be the same or bigger than the device block size). > I still not able to find where sd register its request queue to file > system. It doesn't. The Filesystem registers with block via sys_mount and SCSI with block in scsi_lib.c:scsi_alloc_queue(). James -- 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
