Kernel 6.8.0-20-generic - lowlatency and generic merge into one

**Doug S** · 4 Weeks Ago

Finally, as of the just released kernel 6.8.0-20-generic, the low latency kernel configuration has been put into the generic kernel.
The kernel configuration differences are:

Code:

doug@s19:~/kernel/linux$ scripts/diffconfig /boot/config-6.8.0-11-generic /boot/config-6.8.0-20-generic
-GCC11_NO_ARRAY_BOUNDS y
-TICK_CPU_ACCOUNTING y
 CC_VERSION_TEXT "x86_64-linux-gnu-gcc-13 (Ubuntu 13.2.0-13ubuntu1) 13.2.0" -> "x86_64-linux-gnu-gcc-13 (Ubuntu 13.2.0-19ubuntu1) 13.2.0"
 CONSOLE_LOGLEVEL_QUIET 4 -> 3
 HZ 250 -> 1000
 HZ_1000 n -> y
 HZ_250 y -> n
 INTEL_IOMMU_DEFAULT_ON n -> y
 INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON n -> y
 LATENCYTOP n -> y
 NO_HZ_FULL n -> y
 NO_HZ_IDLE y -> n
 VERSION_SIGNATURE "Ubuntu 6.8.0-11.11-generic 6.8.0-rc4" -> "Ubuntu 6.8.0-20.20-generic 6.8.1"
 VIRT_CPU_ACCOUNTING_GEN n -> y
+CONTEXT_TRACKING_USER y
+CONTEXT_TRACKING_USER_FORCE n
+CRYPTO_DEV_QAT_ERROR_INJECTION n
+DRM_NOUVEAU_GSP_DEFAULT n
+GCC10_NO_ARRAY_BOUNDS y
+GCC_ASM_GOTO_OUTPUT_WORKAROUND y
+HDC3020 m
+MITIGATION_RFDS y
+RCU_LAZY y
+RCU_LAZY_DEFAULT_OFF y
+RCU_NOCB_CPU y
+RCU_NOCB_CPU_DEFAULT_ALL n
+VIRT_CPU_ACCOUNTING y

Users should be aware and watch for anything odd.
I am very happy about this change and think it is years overdue.

I do wonder about this difference between lowlatency and the new combined:

Code:

doug@s19:~/kernel/linux$ scripts/diffconfig /boot/config-6.8.0-7-lowlatency /boot/config-6.8.0-20-generic
...
 PREEMPT y -> n
 PREEMPT_VOLUNTARY n -> y
...

References:
https://bugs.launchpad.net/ubuntu/+s...x/+bug/2051342
https://www.phoronix.com/news/Ubuntu-Generic-LL-Kernel
https://discourse.ubuntu.com/t/enabl...or-24-04/42255

**1fallen** · 4 Weeks Ago

Originally Posted by Doug S

Users should be aware and watch for anything odd.
I am very happy about this change and think it is years overdue.

I do wonder about this difference between lowlatency and the new combined:

That makes two of us on both statements:

Code:

root@me-on-zfs:/sys/kernel/tracing# tail -10 trace
          <idle>-0       [007] d.h1.  2313.235147: #167376 context    irq timer_latency      6795 ns
           <...>-47436   [007] ....1  2313.235152: #167376 context thread timer_latency     10985 ns
          <idle>-0       [008] d.h1.  2313.235178: #167376 context    irq timer_latency      6589 ns
           <...>-47437   [008] ....1  2313.235182: #167376 context thread timer_latency     10919 ns
          <idle>-0       [009] d.h1.  2313.235216: #167376 context    irq timer_latency      6315 ns
           <...>-47438   [009] ....1  2313.235220: #167376 context thread timer_latency     10576 ns
          <idle>-0       [010] d.h1.  2313.235260: #167376 context    irq timer_latency      6880 ns
           <...>-47439   [010] ....1  2313.235264: #167376 context thread timer_latency     11140 ns
          <idle>-0       [011] d.h1.  2313.235291: #167376 context    irq timer_latency      6465 ns
           <...>-47440   [011] ....1  2313.235295: #167376 context thread timer_latency     10725 ns

And:

Code:

root@me-on-zfs:/sys/kernel/tracing#  echo 500 > osnoise/stop_tracing_total_us
root@me-on-zfs:/sys/kernel/tracing# tail -21 per_cpu/cpu7/trace
           <...>-47436   [007] ....1  2549.953151: #404094 context thread timer_latency     10963 ns
          <idle>-0       [007] d.h1.  2549.954147: #404095 context    irq timer_latency      6944 ns
           <...>-47436   [007] ....1  2549.954151: #404095 context thread timer_latency     10715 ns
          <idle>-0       [007] d.h1.  2549.955147: #404096 context    irq timer_latency      6626 ns
           <...>-47436   [007] ....1  2549.955152: #404096 context thread timer_latency     10956 ns
          <idle>-0       [007] d.h1.  2549.956147: #404097 context    irq timer_latency      6727 ns
           <...>-47436   [007] ....1  2549.956151: #404097 context thread timer_latency     10988 ns
          <idle>-0       [007] d.h1.  2549.957147: #404098 context    irq timer_latency      6409 ns
           <...>-47436   [007] ....1  2549.957151: #404098 context thread timer_latency     10600 ns
          <idle>-0       [007] d.h1.  2549.958148: #404099 context    irq timer_latency      7069 ns
           <...>-47436   [007] ....1  2549.958152: #404099 context thread timer_latency     11330 ns
          <idle>-0       [007] d.h1.  2549.959147: #404100 context    irq timer_latency      6821 ns
           <...>-47436   [007] ....1  2549.959152: #404100 context thread timer_latency     11152 ns
          <idle>-0       [007] d.h1.  2549.960148: #404101 context    irq timer_latency      7132 ns
           <...>-47436   [007] ....1  2549.960152: #404101 context thread timer_latency     10974 ns
          <idle>-0       [007] d.h1.  2549.961147: #404102 context    irq timer_latency      6884 ns
           <...>-47436   [007] ....1  2549.961152: #404102 context thread timer_latency     10586 ns
          <idle>-0       [007] d.h1.  2549.962147: #404103 context    irq timer_latency      6985 ns
           <...>-47436   [007] ....1  2549.962151: #404103 context thread timer_latency     11316 ns
          <idle>-0       [007] d.h1.  2549.963147: #404104 context    irq timer_latency      6737 ns
           <...>-47436   [007] ....1  2549.963152: #404104 context thread timer_latency     11068 ns

I see very little difference between the two

**corradoventu** · 4 Weeks Ago

Kernel 6.8.0-20 released? but on my Noble just updated i'm still on 6.8.0-11 (also on partition with proposed enabled)

**Doug S** · 4 Weeks Ago

Originally Posted by corradoventu

Kernel 6.8.0-20 released? but on my Noble just updated i'm still on 6.8.0-11 (also on partition with proposed enabled)

Yes, I am confused. My Ubuntu 24.04 server updated to kernel 6.8.0-20. However, my Ubuntu 24.04 Desktop VM is still at kernel 6.8.0-11. My Desktop VM is still a mess after the upgrade fiasco that started a few days ago, so I wasn't going to worry about it until after the mess is all sorted.

**corradoventu** · 4 Weeks Ago

Kernel 6.8.0.20 seems rolled back: https://launchpad.net/ubuntu/+source/linux

**deadflowr** · 4 Weeks Ago

Most likely has to do with the fact they are rolling back everything.
Cause is the xz-utils debacle.

**1fallen** · 4 Weeks Ago

Originally Posted by deadflowr

Most likely has to do with the fact they are rolling back everything.
Cause is the xz-utils debacle.

Yep I'm going to trash this install very soon.

Code:

 xz --version
xz (XZ Utils) 5.4.5
liblzma 5.4.5

I got the new kernel on desktop:

Code:

uname -r
6.8.0-20-generic

The bad news:

Code:

apt policy xz-utils
xz-utils:
  Installed: 5.4.5-0.3
  Candidate: 5.4.5-0.3
  Version table:
     5.6.1+really5.4.5-1 100
        100 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 Packages
 *** 5.4.5-0.3 500
        500 http://us.archive.ubuntu.com/ubuntu noble-updates/main amd64 Packages
        100 /var/lib/dpkg/status

**corradoventu** · 4 Weeks Ago

After today updates:

Code:

corrado@corrado-n5-nn-0324:~$ apt policy xz-utils
xz-utils:
  Installed: 5.6.1+really5.4.5-1
  Candidate: 5.6.1+really5.4.5-1
  Version table:
 *** 5.6.1+really5.4.5-1 500
        500 http://archive.ubuntu.com/ubuntu noble/main amd64 Packages
        100 /var/lib/dpkg/status
corrado@corrado-n5-nn-0324:~$ apt changelog xz-utils
xz-utils (5.6.1+really5.4.5-1) unstable; urgency=critical
  * Non-maintainer upload by the Security Team.
  * Revert back to the 5.4.5-0.2 version 
 -- Salvatore Bonaccorso <carnil@debian.org>  Thu, 28 Mar 2024 15:59:38 +0100

But i have kernel 6.8.0-11-generic where did the 6.8.0-20 kernel go?

Edit: discourse.ubuntu.com is down from Yesterday

**dajonaga** · 4 Weeks Ago

Originally Posted by corradoventu

After today updates:

Code:

corrado@corrado-n5-nn-0324:~$ apt policy xz-utils
xz-utils:
  Installed: 5.6.1+really5.4.5-1
  Candidate: 5.6.1+really5.4.5-1
  Version table:
 *** 5.6.1+really5.4.5-1 500
        500 http://archive.ubuntu.com/ubuntu noble/main amd64 Packages
        100 /var/lib/dpkg/status
corrado@corrado-n5-nn-0324:~$ apt changelog xz-utils
xz-utils (5.6.1+really5.4.5-1) unstable; urgency=critical
  * Non-maintainer upload by the Security Team.
  * Revert back to the 5.4.5-0.2 version 
 -- Salvatore Bonaccorso <carnil@debian.org>  Thu, 28 Mar 2024 15:59:38 +0100

But i have kernel 6.8.0-11-generic where did the 6.8.0-20 kernel go?

Edit: discourse.ubuntu.com is down from Yesterday

Now I'm wondering... is that 5.6.1+really5.4.5-1 the latest patched, non vulnerable, "we're good".... version... or not?

**MAFoElffen** · 4 Weeks Ago

Not sure either(???) Upstream Debian also shows that version as the source.

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