netdev - Re: CPU scheduler to TXQ binding? (ixgbe vs. igb)

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 for Android: free password hash cracker in your pocket

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

Message-ID: <1411047689.7106.258.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 18 Sep 2014 06:41:29 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:	Alexander Duyck <alexander.h.duyck@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: CPU scheduler to TXQ binding? (ixgbe vs. igb)

On Thu, 2014-09-18 at 06:33 -0700, Eric Dumazet wrote:

> Note that for TCP, there are packets sent by the process doing the
> send(), or packets sent by cpu doing TX completion (because of TSQ),
> but also packets sent by ACK processing done in the reverse way.
> 
> As Alexander explained, if the ACK packets are delivered into another
> CPU, then you might select another TX queue.
> 
> This is mostly prevented because of ooo_okay logic, meaning that a busy
> bulk flow should stick into a single TX queue, no matter of XPS says.
> 
> A TCP_RR workload is free to chose whatever queue, because every packet
> starting a RR block has the ooo_okay set (As prior data was delivered
> and acknowledged by the opposite peer)
> 

Last but not least, there is the fact that networking stacks use
mod_timer() to arm timers, and that by default, timer migration is on 
( cf /proc/sys/kernel/timer_migration )

We probably should use mod_timer_pinned(), but I could not really see
any difference.



--
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