netdev - Re: [RFC PATCH 0/2] remove netpoll rx support

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Message-ID: <1394540689.21721.21.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 11 Mar 2014 05:24:49 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	xiyou.wangcong@...il.com, mpm@...enic.com, satyam.sharma@...il.com
Subject: Re: [RFC PATCH 0/2] remove netpoll rx support

On Tue, 2014-03-11 at 01:43 -0700, Eric W. Biederman wrote:

> It does seem desirable that netpoll should not drain the rx queues.
> Unfortunately that is not how netpoll is built.  By my quick count
> there are 132 drivers in the kernel that support netpoll.
> 
> Several of them such as the e1000e driver already call dev_kfree_skb_any
> or dev_kfree_skb_irq in their rx paths.  What I am implementing seems to
> be the pattern that the better drivers follow today.
> 
> Furthermore netpoll by it's design depends on the ability to receive
> packets in netpoll_poll_dev.  It is a capability I don't think we have
> ever used in the mainline kernel but it is a capability that is there
> deliberately.  Which means if we want netpoll to not mess with the rx
> path we need to change netpoll.
> 
> 
> If we are willing to change the definition of netpoll this is fixable.
> 
> The big enabler is the fact that calling the napi poll function with a
> budget of 0 means don't perform any rx work.
> 
> Which leads to the following set of changes to netpoll if we are brave.

Well, it cannot be worse than current situation, right ?

I never understood and never enabled CONFIG_NETPOLL_TRAP on any of my
builds, I can tell you.



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