Re: Perf doesn't display kernel symbols anymore (bisected commit 659ad3492b91 ("perf maps: Switch from rbtree to lazily sorted array for addresses"))

[James Clark <james.clark@linaro.org>]

On 16/12/2024 7:01 am, Christophe Leroy wrote:
> Hi,
> 
> I noticed with 6.12 LTS Kernel that perf top and perf record/report 
> don't display kernel symbols anymore, instead it displays the raw 
> address with [unknown] as object.
> 
> After bisect I see that the problem appears with commit 659ad3492b91 
> ("perf maps: Switch from rbtree to lazily sorted array for addresses"). 

Hi Christophe,

You might want to try applying 0b90dfda222e3 as it claims to fix this 
commit. I doubt that will fix your issue but it's worth being sure.

There was also another fix recently that could be related: 23c44f6c83

Did you try the perf-tools-next branch? Maybe something that's already 
fixed needs to be backported.

Thanks
James


> Previous commit 39d14c0dd650 ("Merge branch 'perf-tools' into perf- 
> tools-next") doesn't exbibit the problem.
> 
> Now:
> 
> # Overhead  Command     Shared Object  Symbol
> # ........  ..........  ............. ......................................
> #
>      80.49%  Coeur main  [unknown]      [k] 0xc005f0f8
>       3.91%  Coeur main  gau            [.] engine_loop.constprop.0.isra.0
>       1.72%  Coeur main  [unknown]      [k] 0xc005f11c
>       1.09%  Coeur main  [unknown]      [k] 0xc01f82c8
>       0.44%  Coeur main  libc.so.6      [.] epoll_wait
>       0.38%  Coeur main  [unknown]      [k] 0xc0011718
>       0.36%  Coeur main  [unknown]      [k] 0xc01f45c0
>       0.22%  Coeur main  libc.so.6      [.] 
> __GI___pthread_enable_asynccancel
>       0.19%  Coeur main  libc.so.6      [.] 
> __GI___pthread_disable_asynccancel
>       0.19%  Coeur main  [unknown]      [k] 0xc0011170
>       0.19%  Coeur main  [unknown]      [k] 0xc019ac64
>       0.19%  Coeur main  [unknown]      [k] 0xc01f54bc
>       0.16%  Coeur main  libc.so.6      [.] read
> 
> Before commit 659ad3492b91 ("perf maps: Switch from rbtree to lazily 
> sorted array for addresses"):
> 
> # Overhead  Command     Shared Object      Symbol
> # ........  ..........  ................. ......................................
> #
>      76.65%  Coeur main  [kernel.kallsyms]  [k] finish_task_switch.isra.0
>       4.26%  Coeur main  gau                [.] 
> engine_loop.constprop.0.isra.0
>       3.69%  Coeur main  [kernel.kallsyms]  [k] do_epoll_wait
>       2.00%  Coeur main  [kernel.kallsyms]  [k] timerfd_read_iter
>       0.96%  Coeur main  [kernel.kallsyms]  [k] ep_start_scan
>       0.87%  Coeur main  [kernel.kallsyms]  [k] __rseq_handle_notify_resume
>       0.79%  Coeur main  [kernel.kallsyms]  [k] system_call_exception
>       0.71%  Coeur main  [kernel.kallsyms]  [k] do_notify_resume
>       0.66%  Coeur main  [kernel.kallsyms]  [k] timerfd_poll
>       0.63%  Coeur main  [kernel.kallsyms]  [k] __copy_tofrom_user
>       0.57%  Coeur main  libc.so.6          [.] read
>       0.52%  Coeur main  [kernel.kallsyms]  [k] ep_item_poll.isra.0
>       0.52%  Coeur main  [kernel.kallsyms]  [k] 
> schedule_hrtimeout_range_clock
>       0.49%  Coeur main  [kernel.kallsyms]  [k] ep_done_scan
>       0.46%  Coeur main  [kernel.kallsyms]  [k] schedule
>       0.46%  Coeur main  libc.so.6          [.] 
> __GI___pthread_disable_asynccancel
> 
> Can you help fixing that ?
> 
> Christophe
>