Re: [linux-next] perf report runtime extremely long

[Thomas Richter <tmricht@linux.ibm.com>]

On 10/29/25 09:03, Thomas Richter wrote:
> Hi all,
> 
> has something changed recently in perf report in linux-next repo?
> 
> I run perf report -i <file> -D | grep something
> on s390 with 2 different kernels:
> 
> master 6.18.0rc3:
> # uname -a
> Linux a35lp67.lnxne.boe 6.18.0-rc3m-perf+ #23 SMP Tue Oct 28 15:53:44 CET 2025 s390x GNU/Linux
> # ll /tmp/perf2-eSso2q-2
> -rw------- 1 root root 8538184 Oct 29 08:44 /tmp/perf2-eSso2q-2
> # time perf report -i/tmp/perf2-eSso2q-2 -D | grep Counter:000 > /dev/null
> 
> real	0m22.262s
> user	0m22.068s
> sys	0m0.200s
> # 
> 
> This runtime is ok for the perf.data file size.
> 
> linux-next:
> # uname -a
> Linux s83lp47.lnxne.boe 6.18.0-20251028.rc3.git141.f7d2388eeec2.63.fc42.s390x+next #1 SMP Tue Oct 28 20:06:13 CET 2025 s390x GNU/Linux
> #ll /tmp/perf2-eSso2q-2
> -rw-------. 1 root root 8538184 Oct 29 08:47 /tmp/perf2-eSso2q-2
> # time perf report -i/tmp/perf2-eSso2q-2 -D | grep Counter:000 > /dev/null
> 
> real	2m53.601s
> user	2m52.938s
> sys	0m0.575s
> #
> 
> Same perf.data file and run time increased from 22 seconds to nearly 300 seconds, roughly 14 times longer
> for the same input!
> 
> Has anybody similar observations?
> 
> Thanks a lot
> 

Ian,

sorry sent button pushed too early...

here is a second try without option -D.

This is much better:

root in 🌐 s83lp47 in ~ 
❯ ll perf1.data 
-rw-------. 1 root root 99692290 Oct 29 16:17 perf1.data

root in 🌐 s83lp47 in ~ 
❯ time perf record -- perf report -i perf1.data  > /dev/null
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.027 MB perf.data (246 samples) ]

real	0m1.097s
user	0m0.082s
sys	0m0.167s

root in 🌐 s83lp47 in ~ 
❯ perf report --stdio
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 246  of event 'cpum_cf/cycles/P'
# Event count (approx.): 307500000
#
# Overhead  Command  Shared Object        Symbol                                            
# ........  .......  ...................  ..................................................
#
     9.35%  perf     perf                 [.] reader__read_event
     4.47%  perf     perf                 [.] perf_env__arch
     2.85%  perf     ld64.so.1            [.] _dl_relocate_object_no_relro
     2.44%  perf     ld64.so.1            [.] _dl_lookup_symbol_x
     2.44%  perf     ld64.so.1            [.] do_lookup_x
     2.44%  perf     perf                 [.] down_read
     2.03%  perf     perf                 [.] hists__findnew_entry
     2.03%  perf     perf                 [.] perf_hpp__is_dynamic_entry
     1.63%  perf     [kernel.kallsyms]    [k] __s390_indirect_jump_r14
     1.63%  perf     [kernel.kallsyms]    [k] format_decode
     1.63%  perf     libc.so.6            [.] cfree@GLIBC_2.2
     1.63%  perf     perf                 [.] evsel__parse_sample
     1.63%  perf     perf                 [.] map__put
     1.63%  perf     perf                 [.] sort__comm_cmp
     1.63%  perf     perf                 [.] thread__put
     1.22%  perf     [kernel.kallsyms]    [k] folio_add_file_rmap_ptes
     1.22%  perf     [kernel.kallsyms]    [k] get_page_from_freelist
     1.22%  perf     ld64.so.1            [.] _dl_name_match_p
     1.22%  perf     perf                 [.] dump_printf
     1.22%  perf     perf                 [.] evlist__event2evsel
     1.22%  perf     perf                 [.] hashmap_find
     1.22%  perf     perf                 [.] perf_session__deliver_event

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

Vorsitzender des Aufsichtsrats: Wolfgang Wendt

Geschäftsführung: David Faller

Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294