RE: [PATCHv2 net-next 04/12] sctp: implement make_datafrag for sctp_stream_interleave

From: Xin Long

Sent: 08 December 2017 16:18

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Alternatively you could preform the dereference in two steps (i.e. declare an si
pointer on the stack and set it equal to asoc->stream.si, then deref
si->make_datafrag at call time.  That will at least give the compiler an
opportunity to preload the first pointer.

You want to save the function pointer itself.

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Another small difference:
  as you can see, comparing to (X), (Y) is using 0x28(%rsp) in the loop,
  instead of %r13.

So that's what I can see from the related generated code.
If 0x848(%r13) is not worse than 0x28(%rsp) for cpu, I think
asoc->stream.si->make_datafrag() is even better. No ?

That code must have far too many life local variables.
Otherwise there's be a caller saved register available.

	David