From: Yunsheng Lin <linyunsheng@huawei.com>
To: Michal Kubecek <mkubecek@suse.cz>
Cc: <davem@davemloft.net>, <kuba@kernel.org>, <olteanv@gmail.com>,
<ast@kernel.org>, <daniel@iogearbox.net>, <andriin@fb.com>,
<edumazet@google.com>, <weiwan@google.com>,
<cong.wang@bytedance.com>, <ap420073@gmail.com>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linuxarm@openeuler.org>, <mkl@pengutronix.de>,
<linux-can@vger.kernel.org>, <jhs@mojatatu.com>,
<xiyou.wangcong@gmail.com>, <jiri@resnulli.us>,
<andrii@kernel.org>, <kafai@fb.com>, <songliubraving@fb.com>,
<yhs@fb.com>, <john.fastabend@gmail.com>, <kpsingh@kernel.org>,
<bpf@vger.kernel.org>, <pabeni@redhat.com>, <mzhivich@akamai.com>,
<johunt@akamai.com>, <albcamus@gmail.com>,
<kehuan.feng@gmail.com>, <a.fatoum@pengutronix.de>,
<atenart@kernel.org>, <alexander.duyck@gmail.com>,
<hdanton@sina.com>, <jgross@suse.com>, <JKosina@suse.com>
Subject: Re: [PATCH net v4 1/2] net: sched: fix packet stuck problem for lockless qdisc
Date: Tue, 20 Apr 2021 10:23:36 +0800 [thread overview]
Message-ID: <51b1ec1f-e4aa-8876-10e8-1ef84f067728@huawei.com> (raw)
In-Reply-To: <20210419235503.eo77f6s73a4d25oh@lion.mk-sys.cz>
On 2021/4/20 7:55, Michal Kubecek wrote:
> On Mon, Apr 19, 2021 at 05:29:46PM +0200, Michal Kubecek wrote:
>>
>> As pointed out in the discussion on v3, this patch may result in
>> significantly higher CPU consumption with multiple threads competing on
>> a saturated outgoing device. I missed this submission so that I haven't
>> checked it yet but given the description of v3->v4 changes above, it's
>> quite likely that it suffers from the same problem.
>
> And it indeed does. However, with the additional patch from the v3
> discussion, the numbers are approximately the same as with an unpatched
> mainline kernel.
>
> As with v4, I tried this patch on top of 5.12-rc7 with real devices.
> I used two machines with 10Gb/s Intel ixgbe NICs, sender has 16 CPUs
> (2 8-core CPUs with HT disabled) and 16 Rx/Tx queues, receiver has
> 48 CPUs (2 12-core CPUs with HT enabled) and 48 Rx/Tx queues.
>
> threads 5.12-rc7 5.12-rc7 + v4 5.12-rc7 + v4 + stop
> 1 25.1% 38.1% 22.9%
> 8 66.2% 277.0% 74.1%
> 16 90.1% 150.7% 91.0%
> 32 107.2% 272.6% 108.3%
> 64 116.3% 487.5% 118.1%
> 128 126.1% 946.7% 126.9%
>
> (The values are normalized to one core, i.e. 100% corresponds to one
> fully used logical CPU.)
>
> So it seems that repeated scheduling while the queue was stopped is
> indeed the main performance issue and that other cases of the logic
> being too pessimistic do not play significant role. There is an
> exception with 8 connections/threads and the result with just this
> series also looks abnormally high (e.g. much higher than with
> 16 threads). It might be worth investigating what happens there and
> what do the results with other thread counts around 8 look like.
Will try to investigate the 8 connections/threads case.
>
> I'll run some more tests with other traffic patterns tomorrow and
> I'm also going to take a closer look at the additional patch.
Thanks for taking the detail testing and looking.
>
> Michal
>
> .
>
next prev parent reply other threads:[~2021-04-20 2:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-16 1:16 [PATCH net v4 0/2] fix packet stuck problem for lockless qdisc Yunsheng Lin
2021-04-16 1:16 ` [PATCH net v4 1/2] net: sched: " Yunsheng Lin
2021-04-19 15:29 ` Michal Kubecek
2021-04-19 23:55 ` Michal Kubecek
2021-04-20 2:23 ` Yunsheng Lin [this message]
2021-04-20 20:34 ` Michal Kubecek
2021-04-21 1:52 ` Yunsheng Lin
2021-04-21 5:31 ` Michal Kubecek
2021-04-21 8:21 ` Yunsheng Lin
2021-04-21 8:44 ` Michal Kubecek
2021-04-21 9:25 ` Yunsheng Lin
2021-04-23 9:42 ` Yunsheng Lin
2021-04-30 3:11 ` Yunsheng Lin
2021-04-30 3:15 ` Yunsheng Lin
2021-04-30 6:28 ` Michal Kubecek
2021-04-16 1:16 ` [PATCH net v4 2/2] net: sched: fix endless tx action reschedule during deactivation Yunsheng Lin
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