Hi Christoph, > The subject line should be > > "st: implement tape statistics" to fit the general scheme. No problem I can fix that easily. > > On Thu, Apr 23, 2015 at 08:06:50AM +0000, Seymour, Shane M wrote: > > Signed-off-by: Shane Seymour <shane.seymour@xxxxxx> > > Tested-by: Shane Seymour <shane.seymour@xxxxxx> > > Tested-by is usually used for other testers, not the patch author. I'll remove that. > Where is the description of what these staistics do and what you need > them for? A patch with just a subject and a signoff is unlikely to get applied. I'll add that. > A lot of the code seems to be duplicates of what we do in block layer > statistics, I wonder if there is any way to share that code? The following two paragraphs are from Kai about that issue from an email a while ago: "The tape driver does not have access to the block device i/o statistics because the tapes are not block devices but character devices. They use the Linux block subsystem enough to do i/o but this does not include access to the statistics counters. ... One alternative is, of course, to tie the st driver more into the Linux block device system. I have looked into this several times but have never seen how to do this in a simple enough way." Some of the statistics I'm trying to implement aren't possible to determine just using the block layer statistics like keeping track of time spent doing other I/O such as tape movement since it's not a read or a write. The other thing is that disk stats measure I/O in sectors but tape drives are character devices. While most I/O to tape probably happens in a multiple of a sector size it doesn't have to and that means that some I/O would be over or under counted when rounded up or down to the sector size. Thanks Shane -- 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
