On 07/13/2015 10:17 PM, Alexei Starovoitov wrote:
...
We cannot check tc actions from pktgen, since they can be added
dynamically.
So I see three options:
1 get rid of burst hack for both RX and TX in pktgen (kills performance)
2 add unlikely(skb_shread) check to few tc actions
3 do nothing
I think 2 isn't that bad after all if properly documented with
"because pktgen is doing this hack for performance" ?
I'm fine with 3 too, since the whole pktgen business is for root
and for kernel hackers who suppose to know what they're doing.
Hmm, one thing for option 3 could be that we add a modinfo tag
"experimental", so that on loading of pktgen module, we trigger
(like in case of staging) ...
add_taint_module(mod, TAINT_CRAP, LOCKDEP_STILL_OK);
... and add a pr_warn() to the user, it may be more visible/clear
than the "Packet Generator (USE WITH CAUTION)" Kconfig title? ;)
It'd be a pity that we'd need the extra atomic read only for the
pktgen case. :/ With regards to option 2, you could hide that behind
a static inline helper wrapped in IS_ENABLED(CONFIG_NET_PKTGEN), but
that is a veeeery ugly workaround/hack as well (and distros might
even ship it nevertheless). I wouldn't be surprised if there are
other usage combinations with pktgen that would crash your box. :/
Best,
Daniel
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