[dm-devel] [PATCH v4 0/7] per-cpu in_flight counters for bio-based drivers

[Mike Snitzer]

On Thu, Dec 06 2018 at 11:41am -0500,
Mike Snitzer <snitzer at redhat.com> wrote:

> Hey,
> 
> This v4 addresses the compile issues on various archs when CONFIG_SMP
> isn't set (by introducing appropriate wrappers in genhd.h)
> 
> Testing with this v4 I was unable to reproduce the issue you reported
> where iostat always reports 0 for avgqu-sz -- but please let me know
> if you still see problems like that.

I ran blktests and both block/017 and block/018 fail due to this
patchset's changes, I'm still trying to grok what the test result is
_saying_ but I'll hopefully get there soon:

block/017 (do I/O and check the inflight counter)            [failed]
    runtime    ...  77.675s
    --- tests/block/017.out     2018-12-06 12:31:21.457936217 -0500
    +++ /home/git/blktests/results/nodev/block/017.out.bad      2018-12-06 12:36:15.735053586 -0500
    @@ -1,14 +1,14 @@
     Running block/017
    -sysfs inflight reads 1
    +sysfs inflight reads 2
     sysfs inflight writes 0
    -sysfs stat 1
    -diskstats 1
    -sysfs inflight reads 1
    ...
    (Run 'diff -u tests/block/017.out /home/git/blktests/results/nodev/block/017.out.bad' to see the entire diff)

# diff -u tests/block/017.out /home/git/blktests/results/nodev/block/017.out.bad
--- tests/block/017.out 2018-12-06 12:31:21.457936217 -0500
+++ /home/git/blktests/results/nodev/block/017.out.bad  2018-12-06 12:51:36.695542332 -0500
@@ -1,14 +1,14 @@
 Running block/017
-sysfs inflight reads 1
+sysfs inflight reads 2
 sysfs inflight writes 0
-sysfs stat 1
-diskstats 1
-sysfs inflight reads 1
-sysfs inflight writes 1
 sysfs stat 2
 diskstats 2
-sysfs inflight reads 0
+sysfs inflight reads 2
+sysfs inflight writes 1
+sysfs stat 3
+diskstats 3
+sysfs inflight reads 1
 sysfs inflight writes 0
-sysfs stat 0
-diskstats 0
+sysfs stat 1
+diskstats 1
 Test complete

block/018 (do I/O and check iostats times)                   [failed]
    runtime    ...  156.073s
    --- tests/block/018.out     2018-12-06 12:31:21.458936217 -0500
    +++ /home/git/blktests/results/nodev/block/018.out.bad      2018-12-06 12:38:51.831116369 -0500
    @@ -1,10 +1,10 @@
     Running block/018
     read 0 s
     write 0 s
    -read 1 s
    +read 2 s
     write 0 s
    -read 1 s
    ...
    (Run 'diff -u tests/block/018.out /home/git/blktests/results/nodev/block/018.out.bad' to see the entire diff)

# diff -u tests/block/018.out /home/git/blktests/results/nodev/block/018.out.bad
--- tests/block/018.out 2018-12-06 12:31:21.458936217 -0500
+++ /home/git/blktests/results/nodev/block/018.out.bad  2018-12-06 12:38:51.831116369 -0500
@@ -1,10 +1,10 @@
 Running block/018
 read 0 s
 write 0 s
-read 1 s
+read 2 s
 write 0 s
-read 1 s
-write 1 s
 read 2 s
+write 1 s
+read 6 s
 write 3 s
 Test complete