On Tue, Jul 2, 2019 at 6:25 AM Hou Tao <houtao1@xxxxxxxxxx> wrote: > > Hi, > > There are so many io counters, stats and flags in md, so I think > export these info to userspace will be helpful for online-debugging, > especially when the vmlinux file and the crash utility are not > available. And these info can also be utilized during code > understanding. > > MD has already exported some stats through sysfs files under > /sys/block/mdX/md, but using sysfs file to export more internal > stats are not a good choice, because we need to create a single > sysfs file for each internal stat according to the use convention > of sysfs and there are too many internal stats. Further, the > newly-created sysfs files would become APIs for userspace tools, > but that is not we wanted, because these files are related with > internal stats and internal stats may change from time to time. > > And I think debugfs is a better choice. Because we can show multiple > related stats in a debugfs file, and the debugfs file will never be > used as an userspace API. > > Two debugfs files are created to expose these internal stats: > * iostat: io counters and io related stats (e.g., mddev->active_io, > r1conf->nr_pending, or r1confi->retry_list) > * stat: normal stats/flags (e.g., mddev->recovery, conf->array_frozen) > > Because internal stats are spreaded all over md-core and md-personality, > so both md-core and md-personality will create these two debugfs files > under different debugfs directory. > > Patch 1 factors out the debugfs files creation routine for md-core and > md-personality, patch 2 creates two debugfs files: iostat & stat under > /sys/kernel/debug/block/mdX for md-core, and patch 3 creates two debugfs > files: iostat & stat under /sys/kernel/debug/block/mdX/raid1 for md-raid1. > > The following lines show the hierarchy and the content of these debugfs > files for a RAID1 device: > > $ pwd > /sys/kernel/debug/block/md0 > $ tree > . > ├── iostat > ├── raid1 > │ ├── iostat > │ └── stat > └── stat > > $ cat iostat > active_io 0 > sb_wait 0 pending_writes 0 > recovery_active 0 > bitmap pending_writes 0 > > $ cat stat > flags 0x20 > sb_flags 0x0 > recovery 0x0 > > $ cat raid1/iostat > retry_list active 0 > bio_end_io_list active 0 > pending_bio_list active 0 cnt 0 > sync_pending 0 > nr_pending 0 > nr_waiting 0 > nr_queued 0 > barrier 0 Hi, Sorry for the late reply. I think these information are really debug information that we should not show in /sys. Once we expose them in /sys, we need to support them because some use space may start searching data from them. Thanks, Song -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
