From: Ilya Maximets <i.maximets@ovn.org>
To: jean.tourrilhes@hpe.com, Ilya Maximets <i.maximets@ovn.org>
Cc: Tonghao Zhang <xiangxia.m.yue@gmail.com>,
Pravin B Shelar <pshelar@ovn.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Andy Zhou <azhou@ovn.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
ovs dev <dev@openvswitch.org>, William Tu <u9012063@gmail.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Davide Caratti <dcaratti@redhat.com>
Subject: Re: [PATCH net] openvswitch: meter: remove rate from the bucket size calculation
Date: Wed, 28 Apr 2021 20:59:06 +0200 [thread overview]
Message-ID: <22e48984-e0f3-b7d7-9f65-68e93c846c73@ovn.org> (raw)
In-Reply-To: <20210428163124.GA28950@labs.hpe.com>
On 4/28/21 6:31 PM, Jean Tourrilhes wrote:
> On Wed, Apr 28, 2021 at 01:22:12PM +0200, Ilya Maximets wrote:
>>
>> I didn't test it, but I looked at the implementation in
>> net/sched/act_police.c and net/sched/sch_tbf.c, and they should work
>> in a same way as this patch, i.e. it's a classic token bucket where
>> burst is a burst and nothing else.
>
> Actually, act_police.c and sch_tbf.c will behave completely
> differently, even if they are both based on the token bucket
> algorithm.
> The reason is that sch_tbf.c is applied to a queue, and the
> queue will smooth out traffic and avoid drops. The token bucket is
> used to dequeue the queue, this is sometime called leaky bucket. I've
> personally used sch_tbf.c with burst size barely bigger than the MTU,
> and it works fine.
Makes sense. Thanks for the clarification!
> This is why I was suggesting to compare to act_police.c, which
> does not have a queue to smooth out traffic and can only drop
> packets.
I see. Unfortunately, due to the fact that act_police.c uses time
instead of bytes as a measure for tokens, we will still see a difference
in behavior. Probably, not so big, but it will be there and it will
depend on a line rate.
> I believe OVS meters are similar to policers, so that's why
> they are suprising for people used to queues such as TBF and HTB.
>
> Regards,
>
> Jean
>
next prev parent reply other threads:[~2021-04-28 18:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-21 13:57 [PATCH net] openvswitch: meter: remove rate from the bucket size calculation Ilya Maximets
2021-04-23 20:10 ` patchwork-bot+netdevbpf
2021-04-28 6:24 ` Tonghao Zhang
2021-04-28 6:45 ` Jean Tourrilhes
2021-04-28 11:22 ` Ilya Maximets
2021-04-28 16:31 ` Jean Tourrilhes
2021-04-28 18:59 ` Ilya Maximets [this message]
2021-04-29 21:15 ` Ilya Maximets
2021-04-29 21:12 ` Ilya Maximets
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