While we are speaking about all the drawbacks of LTO, it's still not clear what the benefits are? In the very first mail Matthias mentioned that there might be performance improvements but that performance is not the main driving factor behind this initiative. So is it the reduced code size (Matthias mentioned something around ~10%)?
It would be nice to see some real numbers on various platform for both, the performance improvements for native parts like JIT/GC as well as for the size reduction. Aleksei Voitylov <aleksei.voity...@bell-sw.com> schrieb am Di., 14. Jan. 2020, 09:54: > > On 14/01/2020 19:57, Baesken, Matthias wrote: > > Hello Magnus and Aleksei, thanks for the input . > > > > The times you provided really look like they make a big difference at > least for people often building minimal-vm . > > Guess I have to measure myself a bit (maybe the difference is not that > big on our linux s390x / ppc64(le) ) . > > > >> If the change to enable lto by default is proposed, what would be the > >> recommended strategy for development? > >> > > Probably we should a) do not enable it by default but just make sure > it can be enabled easily and works for the minimal-vm > That would be welcome. I have high hopes to LTO the VM some time by > default, and the tendency observed is that the compiler time overhead > for GCC becomes smaller. At the same time there is no reason why vendors > that invested in testing and can absorb the build time hit could provide > binaries with LTO built VMs by passing an additional option flag. > > or b) take it easy to disable it for local development. > > > > Best regards, Matthias > > > > > > > >> Magnus, Matthias, > >> > >> for me, lto is a little heavyweight for development. x86_64 build time > >> with gcc 7: > >> > >> Server 1m32.484s > >> Server+Minimal 1m42.166s > >> Server+Minimal (--with-jvm-features="link-time-opt") 5m29.422s > >> > >> If the change to enable lto by default is proposed, what would be the > >> recommended strategy for development? > >> > >> For ARM32 Minimal, please keep in mind that it's not uncommon to disable > >> LTO plugin in commodity ARM32 gcc compiler distributions, so for some it > >> does not matter what settings we have in OpenJDK. I believe there could > >> be other reasons for that on top of build time (bugs?). > >> > >