=== test ===

standard openSUSE xxhash packages of today

$ make
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.24user 6.69system 0:13.69elapsed 72%CPU (0avgtext+0avgdata 3824maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps
14:04 f3:../xx/xxhash $ make
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.29user 6.05system 0:13.04elapsed 71%CPU (0avgtext+0avgdata 3720maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps
14:05 f3:../xx/xxhash $ make
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.20user 6.29system 0:13.19elapsed 72%CPU (0avgtext+0avgdata 3664maxresident)k
0inputs+0outputs (0major+177minor)pagefaults 0swaps
14:05 f3:../xx/xxhash $ make
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.38user 5.91system 0:12.89elapsed 72%CPU (0avgtext+0avgdata 3712maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps

Mean/Spread: 13.20 ± 0.31 sec (2.3% error)


=== switch packages ===

# rpm -U ...


=== verify AVX512 is now in use ===

Watch this space closely.

$ gdb xh
Reading symbols from xh...
(gdb) b main
Breakpoint 1 at 0x4010b0: file xh.cpp, line 7.
(gdb) r <xh.cpp
Starting program: /home/jengelh/obs_nosave/zu/home/jengelh/xx/xxhash/xh <xh.cpp
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 1, main () at xh.cpp:7
7               auto state = XXH3_createState();
(gdb) b XXH_setDispatch
Breakpoint 2 at 0x7ffff7f9a6f4: file /usr/src/debug/xxHash-0.8.2/xxh_x86dispatch.c, line 706.
(gdb) r
Restart?-yes
Starting program: /home/jengelh/obs_nosave/zu/home/jengelh/xx/xxhash/xh <xh.cpp
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 2, XXH_setDispatch () at /usr/src/debug/xxHash-0.8.2/xxh_x86dispatch.c:706
706     {
(gdb) bt
#0  XXH_setDispatch () at /usr/src/debug/xxHash-0.8.2/xxh_x86dispatch.c:706
#1  0x00007ffff7fca53e in call_init (env=0x7fffffffd998, argv=0x7fffffffd988, argc=1, l=<optimized out>) at dl-init.c:74
#2  call_init (l=<optimized out>, argc=1, argv=0x7fffffffd988, env=0x7fffffffd998) at dl-init.c:26
#3  0x00007ffff7fca63c in _dl_init (main_map=0x7ffff7fbe000, argc=1, argv=0x7fffffffd988, env=0x7fffffffd998) at dl-init.c:121
#4  0x00007ffff7fe2ba0 in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
#5  0x0000000000000001 in ?? ()
#6  0x00007fffffffde8c in ?? ()
#7  0x0000000000000000 in ?? ()
(gdb) n
707         int vecID = XXH_featureTest();
(gdb) 
719         XXH_g_dispatch = XXH_kDispatch[vecID];
(gdb) p vecID
$1 = 3  [= XXH_AVX512!]


=== test ===

$ make test
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.37user 6.16system 0:13.23elapsed 72%CPU (0avgtext+0avgdata 3708maxresident)k
0inputs+0outputs (0major+177minor)pagefaults 0swaps
14:07 f3:../xx/xxhash $ make test
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.23user 6.27system 0:13.27elapsed 71%CPU (0avgtext+0avgdata 3664maxresident)k
0inputs+0outputs (0major+176minor)pagefaults 0swaps
14:07 f3:../xx/xxhash $ make test
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.26user 6.77system 0:13.75elapsed 73%CPU (0avgtext+0avgdata 3712maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps
14:07 f3:../xx/xxhash $ make test
cat linux-6.*.tar{,,,,,,,} | time ./xh
5df8e93736b5a2bddd0b324a455b61fc
3.19user 6.07system 0:12.96elapsed 71%CPU (0avgtext+0avgdata 3712maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps

Mean/Spread: 13.30 ± 0.34s (2.5% error)

== Lessons learned ==

Prerequisite for good measurement:
 * consistent(!) error rate  (4 individual measurements is a bit on the low side, but ... anyway)

Result:
 * The observed 13.2s mean is within the margin of measurement error of the 13.3 mean and viceversa

Conclusion:
 * DISPATCH=1 made no impact on this machine