On 11/26/14 2:36 PM, Mike Hommey wrote: > On Wed, Nov 26, 2014 at 08:48:05AM -0800, Gregory Szorc wrote: >> In the high-level approach, you recognize what the final output is and jump >> straight to fetching that. e.g. if all you really need is libxul, you'll >> fetch libxul.so. None of this intermediary .o files foo. >> >> Different audiences benefit from the different approaches. >> >> Firefox desktop, Fennec, and FxOS developers benefit mostly from a >> high-level approach, as they don't normally care about changing C++. They >> can jump straight to the end without paying a penalty of dealing with >> intermediaries. >> >> Gecko/C++ developers care about the low-level approach, as they'll be >> changing C++ things that invalidate the final output, so they'll be fetching >> intermediate objects out of necessity. >> >> Implementing an effective cache either way relies on several factors: >> >> * For a high-level cache, a build system capable of skipping intermediates >> to fetch the final entity (notably *not* make). >> * Consistent build environments across release automation and developer >> machines (otherwise the binaries are different and you sacrifice cache hit >> rate or "accuracy"). >> * People having fast internet connections to the cache (round trips don't >> take longer than building locally). >> * Fixing C++ header dependency hell so when C++ developers change something >> locally, it doesn't invalidate the world, causing excessive cache misses and >> local computation. >> * Writing to a globally distributed cache that is also read by release >> automation has some fun security challenges. >> * Having a database to correlate source tree state with build artifacts *or* >> a build system that is able to compute the equivalent DAG to formulate a >> cache key (something we can't do today). > > Does the audience that needs high-level cache actually need a cache > /that/ accurate? I wager using nightly builds would work for the vast > majority of cases. We "just" need a build mode that doesn't build code, > which we kinda sorta have, but it's broken at the moment (bug 1063880).
I agree: last Nightly is probably sufficient for most use cases. I would happily build this mode into the build system if I had time. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
