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Message-ID: <f977c0ab-76f5-4869-9fb7-e111104e2fff@kernel.org> Date: Tue, 7 Jan 2025 15:26:35 +0100 From: Jesper Dangaard Brouer <hawk@...nel.org> To: Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com Cc: liuyonglong@...wei.com, fanghaiqing@...wei.com, zhangkun09@...wei.com, Alexander Lobakin <aleksander.lobakin@...el.com>, Robin Murphy <robin.murphy@....com>, Alexander Duyck <alexander.duyck@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, IOMMU <iommu@...ts.linux.dev>, MM <linux-mm@...ck.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, Matthias Brugger <matthias.bgg@...il.com>, AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org Subject: Re: [PATCH net-next v6 0/8] fix two bugs related to page_pool On 06/01/2025 14.01, Yunsheng Lin wrote: > This patchset fix a possible time window problem for page_pool and > the dma API misuse problem as mentioned in [1], and try to avoid the > overhead of the fixing using some optimization. > > From the below performance data, the overhead is not so obvious > due to performance variations 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 > [ 323.367627] bench_page_pool_simple: Loaded > [ 323.448747] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076997150 sec time_interval:76997150) - (invoke count:100000000 tsc_interval:7699707) > [ 324.812884] time_bench: Type:atomic_inc Per elem: 1 cycles(tsc) 13.468 ns (step:0) - (measurement period time:1.346855130 sec time_interval:1346855130) - (invoke count:100000000 tsc_interval:134685507) > [ 324.980875] time_bench: Type:lock Per elem: 1 cycles(tsc) 15.010 ns (step:0) - (measurement period time:0.150101270 sec time_interval:150101270) - (invoke count:10000000 tsc_interval:15010120) > [ 325.652195] time_bench: Type:rcu Per elem: 0 cycles(tsc) 6.542 ns (step:0) - (measurement period time:0.654213000 sec time_interval:654213000) - (invoke count:100000000 tsc_interval:65421294) > [ 325.669215] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path > [ 325.974848] time_bench: Type:no-softirq-page_pool01 Per elem: 2 cycles(tsc) 29.633 ns (step:0) - (measurement period time:0.296338200 sec time_interval:296338200) - (invoke count:10000000 tsc_interval:29633814) (referring to above line, below) > [ 325.993517] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path > [ 326.576636] time_bench: Type:no-softirq-page_pool02 Per elem: 5 cycles(tsc) 57.391 ns (step:0) - (measurement period time:0.573911820 sec time_interval:573911820) - (invoke count:10000000 tsc_interval:57391174) > [ 326.595307] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path > [ 328.422661] time_bench: Type:no-softirq-page_pool03 Per elem: 18 cycles(tsc) 181.849 ns (step:0) - (measurement period time:1.818495880 sec time_interval:1818495880) - (invoke count:10000000 tsc_interval:181849581) > [ 328.441681] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path > [ 328.449584] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path > [ 328.755031] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 2 cycles(tsc) 29.632 ns (step:0) - (measurement period time:0.296327910 sec time_interval:296327910) - (invoke count:10000000 tsc_interval:29632785) It is strange that fast-path "tasklet_page_pool01_fast_path" isn't faster than above "no-softirq-page_pool01". They are both 29.633 ns. What hardware is this? e.g. the cycle count of 2 cycles(tsc) seem strange. On my testlab hardware Intel CPU E5-1650 v4 @3.60GHz My fast-path numbers say 5.202 ns (18 cycles) for "tasklet_page_pool01_fast_path" Raw data look like this [Tue Jan 7 15:15:18 2025] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path [Tue Jan 7 15:15:18 2025] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path [Tue Jan 7 15:15:18 2025] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 18 cycles(tsc) 5.202 ns (step:0) - (measurement period time:0.052020430 sec time_interval:52020430) - (invoke count:10000000 tsc_interval:187272981) [Tue Jan 7 15:15:18 2025] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path [Tue Jan 7 15:15:19 2025] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 55 cycles(tsc) 15.343 ns (step:0) - (measurement period time:0.153438301 sec time_interval:153438301) - (invoke count:10000000 tsc_interval:552378168) [Tue Jan 7 15:15:19 2025] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path [Tue Jan 7 15:15:19 2025] time_bench: Type:tasklet_page_pool03_slow Per elem: 243 cycles(tsc) 67.725 ns (step:0) - (measurement period time:0.677255574 sec time_interval:677255574) - (invoke count:10000000 tsc_interval:2438124315) > [ 328.774308] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path > [ 329.578579] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 7 cycles(tsc) 79.523 ns (step:0) - (measurement period time:0.795236560 sec time_interval:795236560) - (invoke count:10000000 tsc_interval:79523650) > [ 329.597769] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path > [ 331.507501] time_bench: Type:tasklet_page_pool03_slow Per elem: 19 cycles(tsc) 190.104 ns (step:0) - (measurement period time:1.901047510 sec time_interval:1901047510) - (invoke count:10000000 tsc_interval:190104743) > > After this patchset: > root@(none)$ insmod bench_page_pool_simple.ko > [ 138.634758] bench_page_pool_simple: Loaded > [ 138.715879] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076972720 sec time_interval:76972720) - (invoke count:100000000 tsc_interval:7697265) > [ 140.079897] time_bench: Type:atomic_inc Per elem: 1 cycles(tsc) 13.467 ns (step:0) - (measurement period time:1.346735370 sec time_interval:1346735370) - (invoke count:100000000 tsc_interval:134673531) > [ 140.247841] time_bench: Type:lock Per elem: 1 cycles(tsc) 15.005 ns (step:0) - (measurement period time:0.150055080 sec time_interval:150055080) - (invoke count:10000000 tsc_interval:15005497) > [ 140.919072] time_bench: Type:rcu Per elem: 0 cycles(tsc) 6.541 ns (step:0) - (measurement period time:0.654125000 sec time_interval:654125000) - (invoke count:100000000 tsc_interval:65412493) > [ 140.936091] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path > [ 141.246985] time_bench: Type:no-softirq-page_pool01 Per elem: 3 cycles(tsc) 30.159 ns (step:0) - (measurement period time:0.301598160 sec time_interval:301598160) - (invoke count:10000000 tsc_interval:30159812) > [ 141.265654] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path > [ 141.976265] time_bench: Type:no-softirq-page_pool02 Per elem: 7 cycles(tsc) 70.140 ns (step:0) - (measurement period time:0.701405780 sec time_interval:701405780) - (invoke count:10000000 tsc_interval:70140573) > [ 141.994933] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path > [ 144.018945] time_bench: Type:no-softirq-page_pool03 Per elem: 20 cycles(tsc) 201.514 ns (step:0) - (measurement period time:2.015141210 sec time_interval:2015141210) - (invoke count:10000000 tsc_interval:201514113) > [ 144.037966] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path > [ 144.045870] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path > [ 144.205045] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 1 cycles(tsc) 15.005 ns (step:0) - (measurement period time:0.150056510 sec time_interval:150056510) - (invoke count:10000000 tsc_interval:15005645) This 15.005 ns looks like a significant improvement over 29.633 ns > [ 144.224320] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path > [ 144.916044] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 6 cycles(tsc) 68.269 ns (step:0) - (measurement period time:0.682693070 sec time_interval:682693070) - (invoke count:10000000 tsc_interval:68269300) > [ 144.935234] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path > [ 146.997684] time_bench: Type:tasklet_page_pool03_slow Per elem: 20 cycles(tsc) 205.376 ns (step:0) - (measurement period time:2.053766310 sec time_interval:2053766310) - (invoke count:10000000 tsc_interval:205376624) > Looks like I should also try out this patchset on my testlab, as this hardware seems significantly different than mine... > 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel.org/T/ > > CC: Alexander Lobakin <aleksander.lobakin@...el.com> > CC: Robin Murphy <robin.murphy@....com> > CC: Alexander Duyck <alexander.duyck@...il.com> > CC: Andrew Morton <akpm@...ux-foundation.org> > CC: IOMMU <iommu@...ts.linux.dev> > CC: MM <linux-mm@...ck.org> > > Change log: > V6: > 1. Repost based on latest net-next. > 2. Rename page_pool_to_pp() to page_pool_get_pp(). > > 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_get_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 | 24 +- > include/net/page_pool/helpers.h | 11 + > include/net/page_pool/types.h | 63 +- > net/core/devmem.c | 4 +- > net/core/netmem_priv.h | 5 +- > net/core/page_pool.c | 660 ++++++++++++++---- > net/core/page_pool_priv.h | 12 +- > 18 files changed, 664 insertions(+), 164 deletions(-) >
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