netdev - Re: [RFC] net: remove busylock

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Date:	Thu, 19 May 2016 11:41:39 -0700
From:	Rick Jones <rick.jones2@....com>
To:	Alexander Duyck <alexander.duyck@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev <netdev@...r.kernel.org>,
	Alexander Duyck <aduyck@...antis.com>
Subject: Re: [RFC] net: remove busylock

On 05/19/2016 11:03 AM, Alexander Duyck wrote:
> On Thu, May 19, 2016 at 10:08 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> With HTB qdisc, here are the numbers for 200 concurrent TCP_RR, on a host with 48 hyperthreads.
...
>>
>> That would be a 8 % increase.
>
> The main point of the busy lock is to deal with the bulk throughput
> case, not the latency case which would be relatively well behaved.
> The problem wasn't really related to lock bouncing slowing things
> down.  It was the fairness between the threads that was killing us
> because the dequeue needs to have priority.

Quibbledrift... While the origins of the netperf TCP_RR test center on 
measuring latency, I'm not sure I'd call 200 of them running 
concurrently a latency test.  Indeed it may be neither fish nor fowl, 
but it will certainly be exercising the basic packet send/receive path 
rather fully and is likely a reasonable proxy for aggregate small packet 
performance.

happy benchmarking,

rick jones