On Wed, Jun 18, 2025 at 5:46 AM Jesper Dangaard Brouer hawk@kernel.org wrote:
Something is off with benchmark numbers compared to the OOT version.
I assume you're comparing my results (my kernel config + my hardware + upstream benchmark) with your results (your kernel config + your hardware + OOT version). The problem may be in OOT vs upstream but it may be just different code/config/hardware.
True I used OOT version.
Just applied this patch, but I get compile error. Because Makefile tries to get kernel headers (net/page_pool/helpers.h) from local Linux installation instead of git tree. This need to be adjusted for patch, such that it builds with src-local/git tree provided headers.
I believe the fix to that is to do:
make KDIR=$(pwd) -C ./tools/testing/selftests/net/bench
I.e. the build files assume you're building the test to run it on the current machine, to cross compile it for a different machine under test, we need to pass explicit KDIR. I've kinda copy-pasted what other TEST_GEN_MODS_DIR= makefiles do. In theory we could do something else but I am guessing the way current TEST_GEN_MODS_DIR does it is the way to go. Does it work for you if you do that?
[...]
Yeah, I actually just checked and I have CONFIG_DEBUG_NET on in my build, and a lot of other debug configs are turned on.
The CONFIG_DEBUG_NET should be low overhead, so I don't expect this to be the root-cause. Other CONFIG options are more likely the issue.
Thank you very much for the tips. Perf report showed the locking was taking forever on my kernel... I had locking debug configs enabled in my build... sorry... with those disabled, I get much more sane results:
[ 185.557293] bench_page_pool: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path [ 185.607873] bench_page_pool: Type:no-softirq-page_pool01 Per elem: 11 cycles(tsc) 4.177 ns (step:0) - (measurement period time:0.041772642 sec time_interval:41772642) - (invoke count:10000000 tsc_interval:112778487) [ 185.627090] bench_page_pool: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path [ 185.826991] bench_page_pool: Type:no-softirq-page_pool02 Per elem: 51 cycles(tsc) 19.117 ns (step:0) - (measurement period time:0.191178107 sec time_interval:191178107) - (invoke count:10000000 tsc_interval:516173586) [ 185.846380] bench_page_pool: time_bench_page_pool03_slow(): Cannot use page_pool fast-path [ 186.479432] bench_page_pool: Type:no-softirq-page_pool03 Per elem: 168 cycles(tsc) 62.469 ns (step:0) - (measurement period time:0.624690697 sec time_interval:624690697) - (invoke count:10000000 tsc_interval:1686656879)
Does this alleviate your concern? Or do you still see an issue here? There is still a delta between our results, on different hardware/configs but results are in a sane range now.