On Thu, Nov 2, 2017 at 3:43 PM, Nico Grunbaum <ngrunb...@mozilla.com> wrote:
> For rr I have an i7 desktop with a base clock of 4.0 Ghz, and for building > I use icecc to distribute the load (or rather I will be again when bug > 1412240[0] is closed). The i9 series has lower base clocks (2.8 Ghz, and > 2.6Ghz for the top SKUs)[1], but high boost clocks of 4.2 Ghz. If I were > to switch over to an i9 for everything, would I see a notable difference in > performance in rr? > Which i7? You should get better CPU efficiency with newer microarchitectures. The i9's we're talking about are based on Skylake-X which is based on Skylake which are the i7-6XXX models in the consumer lines. It isn't enough to compare MHz: you need to also consider microarchitectures, memory, and workload. https://arstechnica.com/gadgets/2017/09/intel-core-i9-7960x-review/2/ has some single-threaded benchmarks. The i7-7700K (Kaby Lake) seems to "win" for single-threaded performance. But the i9's aren't far behind. Not far enough behind to cancel out the benefits of the extra cores IMO. This is because the i9's are pretty aggressive about using turbo. More aggressive than the Xeons. As long as cooling can keep up, the top-end GHz is great and you aren't sacrificing that much perf to have more cores on die. You can counter by arguing that the consumer-grade i7's can yield more speedups via overclocking. But for enterprise uses, having this all built into the chip so it "just works" without voiding warranty is a nice trait :) FWIW, the choice to go with Xeons always bothered me because we had to make an explicit clock vs core trade-off. Building Firefox requires both many cores for compiling and fast cores for linking. Since the i9's turbo so well, we get the best of both worlds. And at a much lower price. Aside from the loss of ECC, it is a pretty easy decision to switch. > -Nico > > [0] https://bugzilla.mozilla.org/show_bug.cgi?id=1412240 Build failure in > libavutil (missing atomic definitions), when building with clang and icecc > > [1] https://ark.intel.com/products/series/123588/Intel-Core-X- > series-Processors > > On 10/27/17 7:50 PM, Robert O'Callahan wrote: > >> BTW can someone forward this entire thread to their friends at AMD so AMD >> will fix their CPUs to run rr? They're tantalizingly close :-/. >> >> Rob >> > > _______________________________________________ > 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
