Messages in this thread | | | From | Vivien Didelot <> | Subject | Re: [PATCH net-next 1/7] net: dsa: hide dsa_uses_tagged_protocol code | Date | Tue, 30 May 2017 11:56:30 -0400 |
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Hi Andrew, David,
David Miller <davem@davemloft.net> writes:
>>> +bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst) >>> +{ >>> + return !!dst->rcv; >>> +} >>> + >> >> You need to be careful here. This is in the hot path. Every frame >> received uses this code. And think about a distro kernel, which might >> have DSA enabled by default, yet is unlikely to have any switches. You >> are adding a function call which can be called millions of times per >> second.... > > Yeah, we really can't make this change. > > This isn't glibc where we're trying to hide the implementation of "FILE *" > behind accessor functions that caller can't see. We inline things when > performance dictates, and it does here.
Thanks for the explanation, this wasn't obvious to me at all. So inline is mandatory here. Would a dereference like "!!dst->tag_ops->rcv" have an significant impact on performance?
Thanks,
Vivien
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