On 7/2/19 9:29 PM, Hou Tao 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, For online-debugging, I'd suggest you have a try eBPF which can be very helpful. -Bob > 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 > > $ cat raid1/stat > array_frozen 0 > > I'm not sure whether the division of internal stats is appropriate and > whether the internal stats in debugfs files are sufficient, so questions > and comments are weclome. > > Regards, > Tao > > Hou Tao (3): > md-debugfs: add md_debugfs_create_files() > md: export inflight io counters and internal stats in debugfs > raid1: export inflight io counters and internal stats in debugfs > > drivers/md/Makefile | 2 +- > drivers/md/md-debugfs.c | 35 ++++++++++++++++++ > drivers/md/md-debugfs.h | 16 +++++++++ > drivers/md/md.c | 65 ++++++++++++++++++++++++++++++++++ > drivers/md/md.h | 1 + > drivers/md/raid1.c | 78 +++++++++++++++++++++++++++++++++++++++++ > drivers/md/raid1.h | 1 + > 7 files changed, 197 insertions(+), 1 deletion(-) > create mode 100644 drivers/md/md-debugfs.c > create mode 100644 drivers/md/md-debugfs.h >
