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smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4YSjRw22mXz22kgr; Wed, 8 Jan 2025 17:34:36 +0800 (CST) Received: from dggpemf200006.china.huawei.com (unknown [7.185.36.61]) by mail.maildlp.com (Postfix) with ESMTPS id 49DF41A016C; Wed, 8 Jan 2025 17:36:51 +0800 (CST) Received: from [10.67.120.129] (10.67.120.129) by dggpemf200006.china.huawei.com (7.185.36.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 8 Jan 2025 17:36:50 +0800 Message-ID: <7d26402a-bcd1-4e5f-bbf1-8b0a433ee8cd@huawei.com> Date: Wed, 8 Jan 2025 17:36:50 +0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v6 0/8] fix two bugs related to page_pool To: Jesper Dangaard Brouer , , , CC: , , , Alexander Lobakin , Robin Murphy , Alexander Duyck , Andrew Morton , IOMMU , MM , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Matthias Brugger , AngeloGioacchino Del Regno , , , , , , References: <20250106130116.457938-1-linyunsheng@huawei.com> Content-Language: en-US From: Yunsheng Lin In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemf200006.china.huawei.com (7.185.36.61) On 2025/1/7 22:26, Jesper Dangaard Brouer wrote: > > > 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? Arm64 server, as the testing module doesn't support arm64, so get_cycles() in [1] is used to do time keeping instead of using x86 asm instruction. 1. https://lore.kernel.org/lkml/caf31b5e-0e8f-4844-b7ba-ef59ed13b74e@arm.com/T/ > > 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 It seems to be some performance variations here. There seems to be some performance variations between doing test using 'taskset -c 0' and with using 'taskset -c 1' too, I didn't get into the detail reason of performance variations yet, as the performance variations seems to exist before this patchset too. > >> [  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... Yes, it would be much appreciated if it is also tested in your testlab.