On 05/05/2016 09:59 AM, Michael Callahan wrote:
On Thu, May 5, 2016 at 9:27 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
Michael Callahan <michaelcallahan@xxxxxx> writes:
Separate out discards from writes counts in /block/diskstats as well as
the disk related /sys stat files.
Sign-off-by: Michael Callahan <michaelcallahan@xxxxxx>
---
The STAT_* macros might be better defined somewhere else.
The part_*_in_flight macros should probably be per_cpu. I mixed up a
patch to test that but they are used awkwardly in drivers/md/dm.c and
accumulating inflights on cpus would be susceptible to overflow errors
on 32 bit machines (increment on one cpu, complete on another, they sum
correctly until one overflows)
This patch adds the new stats to the end of stat and diskstat for more
backwards compatibility. However this patch breaks iostat which will
need to be updated to grab the additional fields. iostat already has
cases for 4 and 11 entries in stat so adding another for 15 should be
easy enough and it's likely that adding these to the end of the file
rather than right after the write stats is unnecessary.
You can't just break iostat. Split the fields out into another file.
Cheers,
Jeff
Would it be better to make a new stat2 file, make discard_stats, or to
patch iostat.c
to handle the new format? It appears that iostat.c already checks for 4 or 11
stat fields and should be easy to extend to check for 15.
If the new format doesn't break iostat (and others), then we don't need
a new file. If it does, we obviously do. We don't tie kernel and app
upgrades together, so asking users to upgrade iostat because it breaks
with a new kernel is not an option.
Don't add a specific discard stats.
--
Jens Axboe
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