netdev - Re: [PATCH net-next v2 1/2] pkt_sched: fq: avoid artificial bursts for clocked flows

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Date:	Wed, 4 Feb 2015 17:56:39 +0000
From:	Kenneth Klette Jonassen <kennetkl@....uio.no>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-next v2 1/2] pkt_sched: fq: avoid artificial bursts
 for clocked flows

>> -	if (tb[TCA_FQ_INITIAL_QUANTUM])
>> -		q->initial_quantum = nla_get_u32(tb[TCA_FQ_INITIAL_QUANTUM]);
>> +	if (tb[TCA_FQ_INITIAL_QUANTUM]) {
>> +		u32 initial_quantum = nla_get_u32(tb[TCA_FQ_INITIAL_QUANTUM]);
>> +
>> +		if (initial_quantum > q->quantum)
>> +			q->initial_quantum = initial_quantum - q->quantum;
>> +		else
>> +			q->initial_quantum = 0;
>> +	}
> 
> Please do not mix patches. This part already have been Acked by me.

The hang fix touches another part of fq. This part is specific to this patch.

> 
> Quite frankly I do not like this patch.

If it is a code issue, please refactor it or point out some specifics.

Thanks for cc’ing me on your related patch (“do not pace pure ack packets”). Note that your patch does not address the core issue that this patch attempts to fix: fq throttling is just broken for small, clocked flows. This not only concerns TCP/SCTP/ARQ acks, but also thin-streams like VoIP and gaming.