On 19/06/2025 06.19, Mina Almasry wrote:
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
Yes, this worked for me.
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?
Yes.
[...]
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)
My results with this patch:
$ sudo ./test_bench_page_pool.sh rmmod: ERROR: Module bench_page_pool is not currently loaded [268960.638885] bench_page_pool: Loaded [268960.684603] bench_page_pool: Type:for_loop Per elem: 1 cycles(tsc) 0.420 ns (step:0) - (measurement period time:0.042037752 sec time_interval:42037752) - (invoke count:100000000 tsc_interval:151336355) [268961.203806] bench_page_pool: Type:atomic_inc Per elem: 18 cycles(tsc) 5.010 ns (step:0) - (measurement period time:0.501077936 sec time_interval:501077936) - (invoke count:100000000 tsc_interval:1803899823) [268961.332771] bench_page_pool: Type:lock Per elem: 39 cycles(tsc) 11.041 ns (step:0) - (measurement period time:0.110410468 sec time_interval:110410468) - (invoke count:10000000 tsc_interval:397481145) [268961.350718] bench_page_pool: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path [268961.425335] bench_page_pool: Type:no-softirq-page_pool01 Per elem: 23 cycles(tsc) 6.571 ns (step:0) - (measurement period time:0.065719390 sec time_interval:65719390) - (invoke count:10000000 tsc_interval:236591475) [268961.444666] bench_page_pool: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path [268961.622103] bench_page_pool: Type:no-softirq-page_pool02 Per elem: 60 cycles(tsc) 16.862 ns (step:0) - (measurement period time:0.168626201 sec time_interval:168626201) - (invoke count:10000000 tsc_interval:607060218) [268961.641608] bench_page_pool: time_bench_page_pool03_slow(): Cannot use page_pool fast-path [268962.387479] bench_page_pool: Type:no-softirq-page_pool03 Per elem: 265 cycles(tsc) 73.739 ns (step:0) - (measurement period time:0.737399722 sec time_interval:737399722) - (invoke count:10000000 tsc_interval:2654665224)
Fast path results: no-softirq-page_pool01 Per elem: 23 cycles(tsc) 6.571 ns
ptr_ring results: no-softirq-page_pool02 Per elem: 60 cycles(tsc) 16.862 ns
slow path results: no-softirq-page_pool03 Per elem: 265 cycles(tsc) 73.739 ns
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.
Now the results a sane and in range :-)
--Jesper