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Message-ID: <f558df7a-d983-4fc5-8358-faf251994d23@kernel.org> Date: Thu, 16 Jan 2025 19:02:59 +0100 From: Jesper Dangaard Brouer <hawk@...nel.org> To: Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com Cc: zhangkun09@...wei.com, liuyonglong@...wei.com, fanghaiqing@...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 v7 0/8] fix two bugs related to page_pool On 16/01/2025 13.52, Yunsheng Lin wrote: > On 2025/1/16 1:40, Jesper Dangaard Brouer wrote: >> >> >> On 15/01/2025 12.33, Yunsheng Lin wrote: >>> On 2025/1/14 22:31, Jesper Dangaard Brouer wrote: >>>> >>>> >>>> On 10/01/2025 14.06, 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. >>>>> >>>> >>>> My benchmarking on x86_64 CPUs looks significantly different. >>>> - CPU: Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz >>>> >>>> Benchmark (bench_page_pool_simple) results from before and after patchset: >>>> >>>> | Test name | Cycles | | |Nanosec | | | % | >>>> | (tasklet_*)| Before | After |diff| Before | After | diff | change | >>>> |------------+--------+-------+----+--------+--------+-------+--------| >>>> | fast_path | 19 | 24 | 5| 5.399 | 6.928 | 1.529 | 28.3 | >>>> | ptr_ring | 54 | 79 | 25| 15.090 | 21.976 | 6.886 | 45.6 | >>>> | slow | 238 | 299 | 61| 66.134 | 83.298 |17.164 | 26.0 | >>>> #+TBLFM: $4=$3-$2::$7=$6-$5::$8=(($7/$5)*100);%.1f >>>> >>>> My above testing show a clear performance regressions across three >>>> different page_pool operating modes. >>> >>> I retested it on arm64 server patch by patch as the raw performance >>> data in the attachment, it seems the result seemed similar as before. >>> >>> Before this patchset: >>> fast_path ptr_ring slow >>> 1. 31.171 ns 60.980 ns 164.917 ns >>> 2. 28.824 ns 60.891 ns 170.241 ns >>> 3. 14.236 ns 60.583 ns 164.355 ns >>> >>> With patch 1-4: >>> 4. 31.443 ns 53.242 ns 210.148 ns >>> 5. 31.406 ns 53.270 ns 210.189 ns >>> >>> With patch 1-5: >>> 6. 26.163 ns 53.781 ns 189.450 ns >>> 7. 26.189 ns 53.798 ns 189.466 ns >>> >>> With patch 1-8: >>> 8. 28.108 ns 68.199 ns 202.516 ns >>> 9. 16.128 ns 55.904 ns 202.711 ns >>> >>> I am not able to get hold of a x86 server yet, I might be able >>> to get one during weekend. >>> >>> Theoretically, patch 1-4 or 1-5 should not have much performance >>> impact for fast_path and ptr_ring except for the rcu_lock mentioned >>> in page_pool_napi_local(), so it would be good if patch 1-5 is also >>> tested in your testlab with the rcu_lock removing in >>> page_pool_napi_local(). >>> >> >> What are you saying? >> - (1) test patch 1-5 >> - or (2) test patch 1-5 but revert patch 2 with page_pool_napi_local() > > patch 1-5 with below applied. > > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -1207,10 +1207,8 @@ static bool page_pool_napi_local(const struct page_pool *pool) > /* Synchronizated with page_pool_destory() to avoid use-after-free > * for 'napi'. > */ > - rcu_read_lock(); > napi = READ_ONCE(pool->p.napi); > napi_local = napi && READ_ONCE(napi->list_owner) == cpuid; > - rcu_read_unlock(); > > return napi_local; > } > Benchmark (bench_page_pool_simple) results from before and after patchset with patches 1-5m and rcu lock removal as requested. | Test name |Cycles | 1-5 | | Nanosec | 1-5 | | % | | (tasklet_*)|Before | After |diff| Before | After | diff | change | |------------+-------+-------+----+---------+--------+--------+--------| | fast_path | 19 | 19 | 0| 5.399 | 5.492 | 0.093 | 1.7 | | ptr_ring | 54 | 57 | 3| 15.090 | 15.849 | 0.759 | 5.0 | | slow | 238 | 284 | 46| 66.134 | 78.909 | 12.775 | 19.3 | #+TBLFM: $4=$3-$2::$7=$6-$5::$8=(($7/$5)*100);%.1f This test with patches 1-5 looks much better regarding performance. --Jesper https://github.com/xdp-project/xdp-project/blob/main/areas/mem/page_pool07_bench_DMA_fix.org#e5-1650-pp01-dma-fix-v7-p1-5 Kernel: - 6.13.0-rc6-pp01-DMA-fix-v7-p1-5+ #5 SMP PREEMPT_DYNAMIC Thu Jan 16 18:06:53 CET 2025 x86_64 GNU/Linux Machine: Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz modprobe bench_page_pool_simple loops=100000000 Raw data: [ 187.309423] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path [ 187.872849] time_bench: Type:no-softirq-page_pool01 Per elem: 19 cycles(tsc) 5.539 ns (step:0) - (measurement period time:0.553906443 sec time_interval:553906443) - (invoke count:100000000 tsc_interval:1994123064) [ 187.892023] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path [ 189.611070] time_bench: Type:no-softirq-page_pool02 Per elem: 61 cycles(tsc) 17.095 ns (step:0) - (measurement period time:1.709580367 sec time_interval:1709580367) - (invoke count:100000000 tsc_interval:6154679394) [ 189.630414] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path [ 197.222387] time_bench: Type:no-softirq-page_pool03 Per elem: 272 cycles(tsc) 75.826 ns (step:0) - (measurement period time:7.582681388 sec time_interval:7582681388) - (invoke count:100000000 tsc_interval:27298499214) [ 197.241926] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path [ 197.249968] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path [ 197.808470] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 19 cycles(tsc) 5.492 ns (step:0) - (measurement period time:0.549225541 sec time_interval:549225541) - (invoke count:100000000 tsc_interval:1977272238) [ 197.828174] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path [ 199.422305] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 57 cycles(tsc) 15.849 ns (step:0) - (measurement period time:1.584920736 sec time_interval:1584920736) - (invoke count:100000000 tsc_interval:5705890830) [ 199.442087] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path [ 207.342120] time_bench: Type:tasklet_page_pool03_slow Per elem: 284 cycles(tsc) 78.909 ns (step:0) - (measurement period time:7.890955151 sec time_interval:7890955151) - (invoke count:100000000 tsc_interval:28408319289)
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