kern/55089: Possible kernel memory leak in radeondrmkms on 9.0

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

>Number:         55089
>Category:       kern
>Synopsis:       Possible kernel memory leak in radeondrmkms on 9.0
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 20 01:35:00 +0000 2020
>Originator:     Izumi Tsutsui
>Release:        NetBSD 9.0
>Organization:
>Environment:
System: NetBSD mirage 9.0 NetBSD 9.0 (GENERIC) #17: Sun Mar 8 12:57:12 JST 2020 tsutsui@mirage:/s/netbsd-9/src/sys/arch/i386/compile/GENERIC i386
Architecture: i386
Machine: i386
>Description:
I noticed 'vmstat -m' shows:
- a number of kmem-96 "Requests" is so large
- "Releases" count is very small

---
Memory resource pool statistics
Name        Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
kmem-96       96   298899    0      131  7114     0  7114  7114     0   inf    0
ffsdino2     256    45037    0        1  2815     0  2815  2815     0   inf    0
kmem-1024   1024    10360    0       36  2581     0  2581  2581     0   inf    0
kmem-768     768    15085    0     6385  2425     0  2425  2425     0   inf  353
vcachepl     196    45645    0        0  2283     0  2283  2283     0   inf    0

 :
---

This can be observed on HD5450 machine, not on Atom N455 netbook.

>How-To-Repeat:
- boot NetBSD/i386 9.0 on HD5450
- start Xorg (with a patch in PR/54782)
- see kmem-96 usage by 'vmstat -m 1 | grep kmem-96' etc.
- perform scrolls (cat large logs, build.sh etc.) on pseudo terminals
  (xterm, kterm, or mlterm etc.)

---
kmem-96       96   288641    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288642    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288648    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288651    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288651    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288651    0      131  6870     0  6870  6870     0   inf    0
kmem-96       96   288659    0      131  6870     0  6870  6870     0   inf    0

[start scroll on other terminal]

kmem-96       96   288705    0      131  6871     0  6871  6871     0   inf    0
kmem-96       96   289505    0      131  6890     0  6890  6890     0   inf    0
kmem-96       96   290537    0      131  6915     0  6915  6915     0   inf    0
kmem-96       96   291363    0      131  6935     0  6935  6935     0   inf    0
kmem-96       96   292165    0      131  6954     0  6954  6954     0   inf    0
kmem-96       96   293017    0      131  6974     0  6974  6974     0   inf    0
kmem-96       96   293871    0      131  6994     0  6994  6994     0   inf    0
kmem-96       96   294756    0      131  7015     0  7015  7015     0   inf    0
kmem-96       96   295668    0      131  7037     0  7037  7037     0   inf    0
kmem-96       96   296561    0      131  7058     0  7058  7058     0   inf    0
kmem-96       96   297456    0      131  7080     0  7080  7080     0   inf    0

[stop scrolling]

kmem-96       96   297462    0      131  7080     0  7080  7080     0   inf    0
kmem-96       96   297462    0      131  7080     0  7080  7080     0   inf    0
kmem-96       96   297757    0      131  7087     0  7087  7087     0   inf    0
^C
---

>Fix:
No idea.

---
Izumi Tsutsui