On Wed, 2020-03-25 at 11:07 +0100, Greg KH wrote: > On Wed, Mar 25, 2020 at 10:02:41AM +0000, Rantala, Tommi T. (Nokia - > FI/Espoo) wrote: > > > > Other people are apparently seeing this too with 4.19: > > https://kudzia.eu/b/2019/09/iostat-x-1-reporting-100-utilization-of-nearly-idle-nvme-drives/ > > > > > > I also see this only in 4.19.y and bisected to this (based on the Fixes > > tag, this should have been taken to 4.14 too...): > > > > commit 6131837b1de66116459ef4413e26fdbc70d066dc > > Author: Omar Sandoval <osandov@xxxxxx> > > Date: Thu Apr 26 00:21:58 2018 -0700 > > > > blk-mq: count allocated but not started requests in iostats inflight > > > > In the legacy block case, we increment the counter right after we > > allocate the request, not when the driver handles it. In both the > > legacy > > and blk-mq cases, part_inc_in_flight() is called from > > blk_account_io_start() right after we've allocated the request. blk-mq > > only considers requests started requests as inflight, but this is > > inconsistent with the legacy definition and the intention in the code. > > This removes the started condition and instead counts all allocated > > requests. > > > > Fixes: f299b7c7a9de ("blk-mq: provide internal in-flight variant") > > Signed-off-by: Omar Sandoval <osandov@xxxxxx> > > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> > > > > > > > > If I get it right, when the disk is idle, and some request is allocated, > > part_round_stats() with this commit will now add all ticks between > > previous I/O and current time (now - part->stamp) to io_ticks. > > > > Before the commit, part_round_stats() would only update part->stamp when > > called after request allocation. > > So this is a "false" reporting? there's really no load? Correct. > > Any thoughts how to best fix this in 4.19? > > I see the io_ticks accounting has been reworked in 5.0, do we need to > > backport those to 4.19, or any ill effects if this commit is reverted in > > 4.19? > > Do you see this issue in 5.4? What's keeping you from moving to 5.4.y? Yes it's fixed in 5.0 and later. Fixing it in 4.19.x would benefit debian stable users too. :-) BTW is the EOL for 4.19 still end of 2020? > And if this isn't a real issue, is that a problem too? > > As you can test this, if you have a set of patches backported that could > resolve it, can you send them to us? Based on quick looks it's solved by this, I'll need to check if it's enough to fix it: commit 5b18b5a737600fd20ba2045f320d5926ebbf341a Author: Mikulas Patocka <mpatocka@xxxxxxxxxx> Date: Thu Dec 6 11:41:19 2018 -0500 block: delete part_round_stats and switch to less precise counting > > thanks, > > greg k-h
