lscpu cache information is incorrect with focal on arm 64-bit platform (ThunderX2)

[Taihsiang Ho]

Platform: Cavium Sabre Marvell ThunderX2

The L1/L2/L3 cache output by "lscpu" is incorrect, and differes from the output with bionic.

[Steps to Reproduce]
1. Install ubuntu server (focal) on Sabre
2. lspci

[Expected Result]
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 32768K

[Actual Result]
L1d cache: 1.8 MiB
L1i cache: 1.8 MiB
L2 cache: 14 MiB
L3 cache: 64 MiB

[More Information]
1. eoan could reproduce this issue.
2. bionic-hwe could not reproduce this issue (5.3.0-46-generic #38~18.04.1-Ubuntu)
3. with focal, check the cpu cache directly from the virtual devices and the cache information looks good:
    $ cat /sys/devices/system/cpu/cpu0/cache/index0/level /sys/devices/system/cpu/cpu0/cache/index0/size
    1
    32K
4. More information about the system which could reproduce the issue:

    ubuntu@apollo:~$ cat /sys/devices/system/cpu/cpu0/cache/index0/level /sys/devices/system/cpu/cpu0/cache/index0/size
    1
    32K
    ubuntu@apollo:~$ uname -a
    Linux apollo 5.4.0-24-generic #28-Ubuntu SMP Thu Apr 9 22:17:51 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux
    ubuntu@apollo:~$ lsb_release -a
    No LSB modules are available.
    Distributor ID: Ubuntu
    Description: Ubuntu Focal Fossa (development branch)
    Release: 20.04
    Codename: focal
    ubuntu@apollo:~$ dpkg -l util-linux
    Desired=Unknown/Install/Remove/Purge/Hold
    | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
    |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
    ||/ Name Version Architecture Description
    +++-==============-===============-============-=================================
    ii util-linux 2.34-0.1ubuntu9 arm64 miscellaneous system utilities
    ubuntu@apollo:~$

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: util-linux 2.34-0.1ubuntu9
ProcVersionSignature: User Name 5.4.0-24.28-generic 5.4.30
Uname: Linux 5.4.0-24-generic aarch64
ApportVersion: 2.20.11-0ubuntu26
Architecture: arm64
CasperMD5CheckResult: skip
Date: Fri Apr 17 16:00:13 2020
SourcePackage: util-linux
UpgradeStatus: No upgrade log present (probably fresh install)

[Mauricio Faria de Oliveira (mfo)]

Hi Taihsiang,

Thanks for reporting this bug.

This is an upstream deliberate change in output format of caches in lscpu.
They introduced the '--caches' option to provide individual/total sizes.

It affects other architectures as well, not just arm64; e.g., amd64.

For example, on my laptop:

Bionic:

$ lscpu | grep cache
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 3072K

Focal:

$ lscpu | grep cache
L1d cache: 64 KiB
L1i cache: 64 KiB
L2 cache: 512 KiB
L3 cache: 3 MiB

On Eoan and later you can use `lscpu --caches` to get all/individual cache information.

Focal:

$ lscpu --caches
NAME ONE-SIZE ALL-SIZE WAYS TYPE LEVEL
L1d 32K 64K 8 Data 1
L1i 32K 64K 8 Instruction 1
L2 256K 512K 4 Unified 2
L3 3M 3M 12 Unified 3

$ lscpu --caches=one-size
ONE-SIZE
     32K
     32K
    256K
      3M

For documentation purposes, this is the PR requesting/discussing it [1], and this is the patch changing it [2].

Since this has been an upstream decision (see PR comments and patch), I guess it's unlikely they'd change it back (even though it broke the previous output convention, as that has been mentioned/acknowledged in the PR.)

This patch has been introduced on 2.34, so Eoan and later have this format change.

Hope this helps,
Mauricio

[1] https://github.com/karelzak/util-linux/issues/663
[2] https://github.com/karelzak/util-linux/commit/e5f721132ec8b8c933a396d8dcb3efcb67854f13

[Taihsiang Ho (tai271828)]

Hi Mauricio, thank you for providing the information that I was not aware of. It's very clear and helpful for me.

Because the ThunderX2 is unavailable for me currently, I verified the output format with Focal on an arm d06 cpu, which is able to reproduce the "issue" (my own host name "scobee"). It is exactly what you have said.