netdev - Re: [RFC PATCH V2 3/8] netback: switch to NAPI + kthread model

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]

Message-ID: <20120117090730.13ae3c6e@nehalam.linuxnetplumber.net>
Date:	Tue, 17 Jan 2012 09:07:30 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Wei Liu <wei.liu2@...rix.com>
Cc:	ian.campbell@...rix.com, netdev@...r.kernel.org,
	xen-devel@...ts.xensource.com, konrad.wilk@...cle.com,
	david.vrabel@...rix.com, paul.durrant@...rix.com
Subject: Re: [RFC PATCH V2 3/8] netback: switch to NAPI + kthread model

On Tue, 17 Jan 2012 13:46:59 +0000
Wei Liu <wei.liu2@...rix.com> wrote:

> This patch implements 1:1 model netback. We utilizes NAPI and kthread
> to do the weight-lifting job:
> 
>   - NAPI is used for guest side TX (host side RX)
>   - kthread is used for guest side RX (host side TX)
> 
> This model provides better scheduling fairness among vifs. It also
> lays the foundation for future work.
> 
> The major defect for the current implementation is that in the NAPI
> poll handler we don't actually disable interrupt. Xen stuff is
> different from real hardware, it requires some other tuning of ring
> macros.
> 
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>

The network receive processing is sensitive to the context it is run in.
Normally it is run in softirq with interrupts enabled. With your code,
the poll routine disables IRQ's which shouldn't be necessary.

Why does xenvif_receive_skb() need to still exist? Couldn't it
just be replaced with call to netif_receive_skb() in one place it is called.
--
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