netdev - Re: [PATCH net-next v4] page_pool: import Jesper's page

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Message-ID: <CAHS8izOhNRNXyAgfuKW1xKb8PTernfer6tJfxG5FZmq7pePjwA@mail.gmail.com>
Date: Wed, 18 Jun 2025 21:19:41 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	Ilias Apalodimas <ilias.apalodimas@...aro.org>, Toke Høiland-Jørgensen <toke@...e.dk>, 
	Ignat Korchagin <ignat@...udflare.com>
Subject: Re: [PATCH net-next v4] page_pool: import Jesper's page_pool benchmark

On Wed, Jun 18, 2025 at 5:46 AM Jesper Dangaard Brouer <hawk@...nel.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.

-- 
Thanks,
Mina