qemu-system-i386 process with sdl, gl=on progressively consumes more and more host cpu?

[Andrew Randrianasulu]

Hello, all!

I use qemu-system-i386/qemu-system_x86_64 for rebuilding Slax-like live cd/dvd.
Usually guests (with various self-compiled kernels and X stack with kde3 on top 
of them)
boot up normally, but if I left them to run in GUI mode for few hours - qemu 
process on host
started to eat more and more cpu for itself - more notiecable if I set host cpu 
to lowest possible
frequency via trayfreq applet (1400Mhz in my case).

Boot line a bit complicated, but I really prefer to have sound and usb inside 
VM.
qemu-system-i386 -cdrom /dev/shm/CDROM-4.4.194_5.iso -m 1.9G -enable-kvm 
-soundhw es1370 -smp 2 -display sdl,gl=on -usb -cpu host -rtc clock=vm

rtc clock=vm was taken from https://bugs.launchpad.net/qemu/+bug/1174654 but 
apparently not helping.
After just 3 hours of uptime (copied line from 'top' on host)

31943 guest     20   0 2412m 791m  38m R   51  6.7  66:36.51 qemu-system-i38

I use Xorg 1.19.7 on host, with mesa git/nouveau as GL driver. But my card has 
not very big amount of VRAM - only 384Mb.
May be this limitation is playing some role .. but 'end-user' result was after 
1-2 day of guest uptime I run into completely frozen guest 
(may be when qemu was hitting 100 one core usage on host some internal timer 
just made guest kernel too upset/froze?
 I was sleeping or doing other things on host  for all this time, with VM just 
supposedly running at another virtual desktop - 
in KDE3 + built-in compositor ....)

I wonder if more mainstream desktop users (on GNOME, Xfce, etc) and/or users of 
other distros (I use self-re-compiled Slackware)
actually can see same problem?

qemu-system-i386 --version
QEMU emulator version 4.1.50 (v4.1.0-1188-gc6f5012ba5-dirty)
but I saw same behavior for quite some time .. just never reported it in hope 
it will go away.

cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 21
model           : 2
model name      : AMD FX(tm)-4300 Quad-Core Processor
stepping        : 0
microcode       : 0x6000852
cpu MHz         : 1399.977
cache size      : 2048 KB
physical id     : 0
siblings        : 4
core id         : 0
cpu cores       : 2
apicid          : 16
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb 
rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf 
pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c 
lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch 
osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core 
perfctr_nb cpb hw_pstate ssbd vmmcall bmi1 arat npt lbrv svm_lock nrip_save 
tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold
bugs            : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 
spec_store_bypass
bogomips        : 7600.06
TLB size        : 1536 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro

[and 3x more of the same, for 3 remaining cores]

Gcc is Slackware 14.2's gcc 5.5.0, but I saw this with 4.9.2 too.
This might be 32-bit host problem. But may be just no-one tried to run qemu 
with GUI guest for literaly days?

Host kernel is
 uname -a
Linux slax 5.1.12-x64 #1 SMP PREEMPT Wed Jun 19 12:31:05 MSK 2019 x86_64 AMD 
FX(tm)-4300 Quad-Core Processor AuthenticAMD GNU/Linux

I was trying newish 5.3.2 but my compilation was not as stable as this one 
(I tend to change few things, like max cpu count, preemption mode, numa support 
.... 
for more distribution-like, yet most stable  and performant for me kernel)

Kernel world is moving fast, so I'll try to recompile new 5.3.x too ....


I guess I  should provide perf/profiler output, but for  this I need to 
recompile qemu. 
I'll try to come back with more details soon.

Thanks for your attention and possible feedback!