On Thu, 2015-02-05 at 18:50 +0000, Bryn M. Reeves wrote: > On Thu, Feb 05, 2015 at 07:46:32PM +0200, "Kai Mäkisara (Kolumbus)" wrote: > > > On 5.2.2015, at 19.40, Laurence Oberman <loberman@xxxxxxxxxx> wrote: > > > From: "Kai Mäkisara (Kolumbus)" <kai.makisara@xxxxxxxxxxx> > > > I still think that the tape statistics should be exported like the statistics of “real” block devices, i.e., one sysfs file exporting on a single line the statistics that temporally belong together. James rejected this approach. I am leaving the decision about this code to him. I will neither ack nor nak this code. > > > > > > I missed the earlier conversations with James, I will go search for them. > > > Do you mean add them so they are similar to the /proc/diskstats > > http://comments.gmane.org/gmane.linux.scsi/80497 > > On Fri, Feb 22 2013 James Bottomley wrote: > >>>> I'm afraid we can't do it the way you're proposing. files in sysfs must > >>>> conform to the one value per file rule (so we avoid the ABI nastiness > >>>> that plagues /proc). You can create a stat directory with a bunch of > >>>> files, but not a single file that gives all values. > > Documentation/filesystems/sysfs.txt does not agree: > > "Attributes should be ASCII text files, preferably with only one value > per file. It is noted that it may not be efficient to contain only one > value per file, so it is socially acceptable to express an array of > values of the same type." > > There's also ample precedent for this: sysfs disk and partition stats, > SELinux cache and hash table stats (which have a pretty yucky 2d int > array with column headers and a name: val format respectively). > > There's also a bunch of multivariate name=value format stats files in > the cgroups sysfs tree. > > > Not exactly. I mean the data exported in sysfs, for example: > > > > > cat /sys/block/sda/sda1/stat > > 159740 9006 5941506 64461 124724 55907 12772208 3598677 0 299875 3663235 > > I'd prefer to consume tape stats in this format too; it follows the > principle of least surprise since it's shared with every other IO stats > source (including device-mapper statistics) and it simplifies handling > the counters in user space. OK, the sysfs bikeshedders hang out on linux-api https://www.kernel.org/doc/man-pages/linux-api-ml.html If you can convince them, we'll do the single file approach. 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
