[RFCv5,0/8] fix two bugs related to page_pool

Message

Yunsheng Lin Dec. 13, 2024, 12:27 p.m. UTC

This version is mainly to see if using page_pool_item metadata
to keep track of all pages is the correct way to fix the dma
API misuse problem.

Note, it is not based on the latest net-next tree yet, but based
on the below commit in net-next:
commit da4fa00abe56 ("Merge branch 'mitigate-the-two-reallocations-issue-for-iptunnels'")

From the below performance data, the overhead is avoided as much as possible
for time_bench_page_pool01_fast_path() and time_bench_page_pool02_ptr_ring,
and there is about 20ns overhead for time_bench_page_pool03_slow() for fixing
the bug.

Before this patchset:
root@(none)$ insmod bench_page_pool_simple.ko
root@(none)$ insmod bench_page_pool_simple.ko
[   67.667196] bench_page_pool_simple: Loaded
[   67.748321] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076977910 sec time_interval:76977910) - (invoke count:100000000 tsc_interval:7697783)
[   69.851812] time_bench: Type:atomic_inc Per elem: 2 cycles(tsc) 20.862 ns (step:0) - (measurement period time:2.086207700 sec time_interval:2086207700) - (invoke count:100000000 tsc_interval:208620764)
[   70.019852] time_bench: Type:lock Per elem: 1 cycles(tsc) 15.015 ns (step:0) - (measurement period time:0.150151600 sec time_interval:150151600) - (invoke count:10000000 tsc_interval:15015154)
[   70.691100] time_bench: Type:rcu Per elem: 0 cycles(tsc) 6.541 ns (step:0) - (measurement period time:0.654142450 sec time_interval:654142450) - (invoke count:100000000 tsc_interval:65414239)
[   70.708119] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path
[   70.975262] time_bench: Type:no-softirq-page_pool01 Per elem: 2 cycles(tsc) 25.785 ns (step:0) - (measurement period time:0.257850110 sec time_interval:257850110) - (invoke count:10000000 tsc_interval:25785005)
[   70.993931] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path
[   71.575053] time_bench: Type:no-softirq-page_pool02 Per elem: 5 cycles(tsc) 57.191 ns (step:0) - (measurement period time:0.571916900 sec time_interval:571916900) - (invoke count:10000000 tsc_interval:57191684)
[   71.593722] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path
[   73.384560] time_bench: Type:no-softirq-page_pool03 Per elem: 17 cycles(tsc) 178.197 ns (step:0) - (measurement period time:1.781979820 sec time_interval:1781979820) - (invoke count:10000000 tsc_interval:178197975)
[   73.403581] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path
[   73.411485] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path
[   73.678410] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 2 cycles(tsc) 25.780 ns (step:0) - (measurement period time:0.257807630 sec time_interval:257807630) - (invoke count:10000000 tsc_interval:25780758)
[   73.697686] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path
[   74.242807] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 5 cycles(tsc) 53.608 ns (step:0) - (measurement period time:0.536089620 sec time_interval:536089620) - (invoke count:10000000 tsc_interval:53608957)
[   74.261996] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path
[   76.115762] time_bench: Type:tasklet_page_pool03_slow Per elem: 18 cycles(tsc) 184.508 ns (step:0) - (measurement period time:1.845082100 sec time_interval:1845082100) - (invoke count:10000000 tsc_interval:184508203)

After this patchset:
root@(none)$ insmod bench_page_pool_simple.ko
[   88.665991] bench_page_pool_simple: Loaded
[   88.747105] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076981170 sec time_interval:76981170) - (invoke count:100000000 tsc_interval:7698109)
[   91.585102] time_bench: Type:atomic_inc Per elem: 2 cycles(tsc) 28.206 ns (step:0) - (measurement period time:2.820699360 sec time_interval:2820699360) - (invoke count:100000000 tsc_interval:282069929)
[   91.753048] time_bench: Type:lock Per elem: 1 cycles(tsc) 15.005 ns (step:0) - (measurement period time:0.150057320 sec time_interval:150057320) - (invoke count:10000000 tsc_interval:15005727)
[   92.424306] time_bench: Type:rcu Per elem: 0 cycles(tsc) 6.541 ns (step:0) - (measurement period time:0.654151520 sec time_interval:654151520) - (invoke count:100000000 tsc_interval:65415145)
[   92.441325] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path
[   92.696225] time_bench: Type:no-softirq-page_pool01 Per elem: 2 cycles(tsc) 24.560 ns (step:0) - (measurement period time:0.245607210 sec time_interval:245607210) - (invoke count:10000000 tsc_interval:24560715)
[   92.714893] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path
[   93.336550] time_bench: Type:no-softirq-page_pool02 Per elem: 6 cycles(tsc) 61.245 ns (step:0) - (measurement period time:0.612451380 sec time_interval:612451380) - (invoke count:10000000 tsc_interval:61245127)
[   93.355219] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path
[   95.402370] time_bench: Type:no-softirq-page_pool03 Per elem: 20 cycles(tsc) 203.828 ns (step:0) - (measurement period time:2.038286740 sec time_interval:2038286740) - (invoke count:10000000 tsc_interval:203828660)
[   95.421395] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path
[   95.429301] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path
[   95.684025] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 2 cycles(tsc) 24.560 ns (step:0) - (measurement period time:0.245605490 sec time_interval:245605490) - (invoke count:10000000 tsc_interval:24560544)
[   95.703301] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path
[   96.401877] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 6 cycles(tsc) 68.954 ns (step:0) - (measurement period time:0.689544160 sec time_interval:689544160) - (invoke count:10000000 tsc_interval:68954410)
[   96.421065] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path
[   98.496283] time_bench: Type:tasklet_page_pool03_slow Per elem: 20 cycles(tsc) 206.653 ns (step:0) - (measurement period time:2.066533210 sec time_interval:2066533210) - (invoke count:10000000 tsc_interval:206653316)

1. https://lore.kernel.org/lkml/[e-mail]/T/

CC: Alexander Lobakin <[e-mail]>
CC: Robin Murphy <[e-mail]>
CC: Alexander Duyck <[e-mail]>
CC: Andrew Morton <[e-mail]>
CC: IOMMU <[e-mail]>
CC: MM <[e-mail]>

Change log:
V5:
  1. Support unlimit inflight pages.
  2. Add some optimization to avoid the overhead of fixing bug.

V4:
  1. use scanning to do the unmapping
  2. spilt dma sync skipping into separate patch

V3:
  1. Target net-next tree instead of net tree.
  2. Narrow the rcu lock as the discussion in v2.
  3. Check the ummapping cnt against the inflight cnt.

V2:
  1. Add a item_full stat.
  2. Use container_of() for page_pool_to_pp().

Yunsheng Lin (8):
  page_pool: introduce page_pool_to_pp() API
  page_pool: fix timing for checking and disabling napi_local
  page_pool: fix IOMMU crash when driver has already unbound
  page_pool: support unlimited number of inflight pages
  page_pool: skip dma sync operation for inflight pages
  page_pool: use list instead of ptr_ring for ring cache
  page_pool: batch refilling pages to reduce atomic operation
  page_pool: use list instead of array for alloc cache

 drivers/net/ethernet/freescale/fec_main.c     |   8 +-
 .../ethernet/google/gve/gve_buffer_mgmt_dqo.c |   2 +-
 drivers/net/ethernet/intel/iavf/iavf_txrx.c   |   6 +-
 drivers/net/ethernet/intel/idpf/idpf_txrx.c   |  14 +-
 drivers/net/ethernet/intel/libeth/rx.c        |   2 +-
 .../net/ethernet/mellanox/mlx5/core/en/xdp.c  |   3 +-
 drivers/net/netdevsim/netdev.c                |   6 +-
 drivers/net/wireless/mediatek/mt76/mt76.h     |   2 +-
 include/linux/mm_types.h                      |   2 +-
 include/linux/skbuff.h                        |   1 +
 include/net/libeth/rx.h                       |   3 +-
 include/net/netmem.h                          |  10 +-
 include/net/page_pool/helpers.h               |  11 +
 include/net/page_pool/types.h                 |  57 +-
 net/core/devmem.c                             |   4 +-
 net/core/netmem_priv.h                        |   5 +-
 net/core/page_pool.c                          | 660 ++++++++++++++----
 net/core/page_pool_priv.h                     |  12 +-
 net/core/skbuff.c                             |   3 +-
 net/core/xdp.c                                |   3 +-
 20 files changed, 650 insertions(+), 164 deletions(-)