On Fri, Dec 08, 2017 at 02:06:04PM +0000, David Laight wrote: > From: Xin Long > > Sent: 08 December 2017 13:04 > ... > > @@ -264,8 +264,8 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct > > sctp_association *asoc, > > frag |= SCTP_DATA_SACK_IMM; > > } > > > > - chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag, > > - 0, GFP_KERNEL); > > + chunk = asoc->stream.si->make_datafrag(asoc, sinfo, len, frag, > > + GFP_KERNEL); > > I know that none of the sctp code is very optimised, but that indirect > call is going to be horrid.
Yeah.. but there is no way to avoid the double derreference considering we only have the asoc pointer in there and we have to reach the contents of the data chunk operations struct, and the .si part is the same as 'stream' part as it's a constant offset. Due to the for() in there, we could add a variable to store asoc->stream.si outside the for and then we can do only a single deref inside it. Xin, can you please try and see if the generated code is different? Other suggestions? Marcelo
