On Wed, Apr 25, 2018 at 10:21 AM, Ted Mielczarek <t...@mielczarek.org> wrote:
> On Wed, Apr 25, 2018, at 12:32 PM, Jeff Muizelaar wrote: > > At minimum we should make --enable-profiling build with rust-opt. > > This sounds reasonable, although the quirk is that we default > --enable-profiling on for nightly[1], so anyone building m-c will have it > enabled. We could make the build system only do this for "explicitly > enabled --enable-profiling", it just might be slightly confusing. (For > reference, the rustc opt level is controlled here[2].) > We could also change this default. In general, Nightly is usually fine for profiling, so I think the set of people doing local builds for profiling is small enough that we could reasonably expect them to set the flag in their mozconfig. > > IIRC the slowdown from using opt-level=2 vs. 1 is primarily in LLVM? It > would probably be useful if we instrumented the build to record compilation > times for all of the crates we build at various optimization levels and see > where the biggest issues are. Perhaps we could get someone on the Rust team > to make some improvements if we know what the worst offenders are. > Well, there's the opt level thing, but there's also the much larger bit that we don't do Rust LTO without --enable-release, which IIUC has a substantial performance impact. > > -Ted > > 1. https://dxr.mozilla.org/mozilla-central/rev/ > 26e53729a10976f52e75efa44e17b5e054969fec/js/moz.configure#243 > 2. https://dxr.mozilla.org/mozilla-central/rev/ > 26e53729a10976f52e75efa44e17b5e054969fec/build/moz. > configure/toolchain.configure#1397 > _______________________________________________ > dev-platform mailing list > dev-platform@lists.mozilla.org > https://lists.mozilla.org/listinfo/dev-platform > _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
