Re: [RFC PATCH 0/5] net: low latency Ethernet device polling

From: Cong Wang
Date: Mon Mar 04 2013 - 02:38:13 EST


On 02/28/2013 01:55 AM, Eliezer Tamir wrote:

Open issues:
1. Find a way to avoid the need to change the sk and skb structs.
One big disadvantage of how we do this right now is that when a device is
removed, it's hard to prevent it from getting polled by a socket
which holds a stale reference.

2. How do we decide which sockets are eligible to do busy polling?
Do we add a socket option to control this?
How do we provide sane defaults while allowing flexibility and performance?

3. Andi Kleen and HPA pointed out that using get_cycles() is not portable.

4. How and where do we call ndo_ll_poll from the socket code?
One good place seems to be wherever the kernel puts the process to sleep,
waiting for more data, but this makes doing something intelligent about
poll (the system call) hard. From the perspective of how ndo_ll_poll
itself is implemented this does not seem to matter.

5. I would like to hear suggestions on naming conventions and where
to put the code that for now I have put in include/net/ll_poll.h



A dumb question: is bypassing tcpdump/netfilters/qdisc etc. what we always want? Isn't this a security issue?

Thanks!
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