page_pool: import Jesper's page_pool benchmark

page_pool: import Jesper's page_pool benchmark

We frequently consult with Jesper's out-of-tree page_pool benchmark to
evaluate page_pool changes.

Import the benchmark into the upstream linux kernel tree so that (a)
we're all running the same version, (b) pave the way for shared
improvements, and (c) maybe one day integrate it with nipa, if possible.

Import bench_page_pool_simple from commit 35b1716d0c30 ("Add
page_bench06_walk_all"), from this repository:
https://github.com/netoptimizer/prototype-kernel.git

Changes done during upstreaming:
- Fix checkpatch issues.
- Remove the tasklet logic not needed.
- Move under tools/testing
- Create ksft for the benchmark.
- Changed slightly how the benchmark gets build. Out of tree, time_bench
  is built as an independent .ko. Here it is included in
  bench_page_pool.ko

Steps to run:

```
mkdir -p /tmp/run-pp-bench
make -C ./tools/testing/selftests/net/bench
make -C ./tools/testing/selftests/net/bench install INSTALL_PATH=/tmp/run-pp-bench
rsync --delete -avz --progress /tmp/run-pp-bench mina@$SERVER:~/
ssh mina@$SERVER << EOF
  cd ~/run-pp-bench && sudo ./test_bench_page_pool.sh
EOF
```

Note that by default, the Makefile will build the benchmark for the
currently installed kernel in /lib/modules/$(shell uname -r)/build. To
build against the current tree, do:

make KDIR=$(pwd) -C ./tools/testing/selftests/net/bench

Output (from Jesper):

```
sudo ./test_bench_page_pool.sh
(benchmark dmesg logs snipped)

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
```

Output (from me):

```
sudo ./test_bench_page_pool.sh
(benchmark dmesg logs snipped)

Fast path results:
no-softirq-page_pool01 Per elem: 11 cycles(tsc) 4.177 ns

ptr_ring results:
no-softirq-page_pool02 Per elem: 51 cycles(tsc) 19.117 ns

slow path results:
no-softirq-page_pool03 Per elem: 168 cycles(tsc) 62.469 ns
```

Results of course will vary based on hardware/kernel/configs, and some
variance may be there from run to run due to some noise.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20250619181519.3102426-1-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>