>On Thu, Apr 02, 2015 at 04:38:13PM +0000, Kavanagh, Mark B wrote: >> >> >On 04/01/15 at 07:45am, Kavanagh, Mark B wrote: >> >> >> >> >What's wrong with setting CFLAGS on the "configure" or "make" command >> >> >line? This is the standard way to do this with Automake and Autoconf. >> >> > >> >> >> >> Sure. However, setting CFLAGS on the command line overwrites any values >> >> CFLAGS has >> >attained via the 'configure' step. The most obvious symptom of this is >> >significantly >> >degraded performance, due to the fact that the optimization flags passed to >> >CFLAGS >during >> >'configure' are overwritten by the command line value of CFLAGS. >> > >> >That should not be the case at all. 9562639 fixed this and stores >> >the flags collected by configure in OVS_CFLAGS while the user can >> >specify his own CFLAGS. >> > >> >If there is a bug, let's fix the bug. >> >> Hi Thomas, >> >> I have little experience of automake, so apologies for any shortcomings in my >understanding in this response. >> >> I've done quite a bit of testing on this, and have observed that >> whenever CFLAGS are passed to 'make' on the command line (building >> against DPDK), the performance degrades by ~3x; this leads me to >> believe that the existing value of CFLAGS (namely -O2 -g) has been >> overwritten by its command line counterpart. > >Yes, if you supply your own CFLAGS then you have to supply -O2 -g, if >you want them. You can leave them out, if you do not want them. Those >are the only CFLAGS that are ever supplied automatically. > >> With respect to 9562639, I don't see where OVS_CFLAGS obtains its >> initial value (i.e. existing CFLAGS). I've made a slight modification, >> and found that it resolves the issue - maybe you could comment as to >> the validity of the changes? > >OVS_CFLAGS is used in addition to CFLAGS, not as a substitute for it, so >it should not include $CFLAGS. > >All of this is the standard way to use Autoconf and Automake. I might >do things differently, if I were to invent my own way of doing things, >since these conventions are somewhat weird in my opinion, but as long as >we continue to use them I think it is best to honor their conventions.
No problem - thanks for updating INSTALL.md :) _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
