Re: [PATCH] Add prefetches in net/ipv4/route.c

[Robert Olsson <Robert.Olsson@xxxxxxxxxxx>]

Rick Jones writes:

 > >  My experiences from playing with prefetching eth_type_trans in this 
 > >  case. One must look in the total performance not just were the 
 > >  prefetching is done. In this case I was able to get eth_type_trans
 > >  down in the profile list but other functions increased so performance
 > >  was the same or lower. This needs to be sorted out... 
 > 
 > How many of the architectures have PMU's that can give us cache miss 
 > statistics? 
 >   Itanium does, and can go so far as to tell us which addresses and 
 > instructions 
 > are involved - do the others?

 I've seem XEON and Opterons has performance counters for this that can 
 be used with oprofile. Intel has a document (was it an application note?) 
 describing prefetching. Really a lot of things to consider to become 
 successful.

 > That sort of data would seem to be desirable in this sort of situation.

 Also what scenario code patch and load we optimizing for Eric mentioned 
 this briefly. 

 Cheers.
                                        --ro