netdev - Re: [PATCH] ifb: add multi-queue support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 13 Nov 2009 07:45:08 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Patrick McHardy <kaber@...sh.net>,
	Tom Herbert <therbert@...gle.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] ifb: add multi-queue support

On 13-11-2009 07:16, Changli Gao wrote:
> 2009/11/13 Eric Dumazet <eric.dumazet@...il.com>:
>> Messy ? Because of few tests added in code, and branches always
>> correctly predicted ?
>>
>> Still some people might rely on tasklet instead of workqueues
>> and added scheduler stress and latency penalty. Tasklet are softirq
>> and normally are processed a few nanosecs later than RX softirq,
>> on the same CPU, while with your workqueue, I guess the scheduler will
>> try to not migrate it, so we add a penalty for light to moderate load.
>>
>> I guess this new ifb mode would be a regression for them ?
>>
>> If you dont want to maintain a compatibility mode, maybe you
>> should introduce a complete new driver, drivers/net/ifbmq.c or ifbwq.c
>>
>> (multiqueue or workqueue references)
>>
> 
> It sounds a good idea.

I don't think so. There would be a lot of code duplication and later
maintenance problems only because of the scheduling method. The main
question is to establish if there is really no performance difference
(which I doubt) - unless Changli can show some tests for various
setups now. On the other hand, if there is a difference, why keep
ineffective solution - similar thing should be possible to do in the
softirq context as well.

So it should not be a big problem to do it a bit messy for some
testing time. Since we can use separate ->ndo_start_xmit() etc. it
shouldn't be too messy, I guess.

Jarek P.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html