On Fri, Jan 19, 2018 at 12:26 AM, victor romanchuk <r...@persimplex.net> wrote: > local:jumbo-build:www-client/chromium: Combine source files to speed up > build process. > > setting that significantly speeds up emerge time (tried it twice; the second > attempt had the flag set) > > $ qlop -gHv -d `date +%Y-%m-%d` chromium > chromium-63.0.3239.132: Fri Jan 19 03:15:43 2018: 1 hour, 47 minutes, 28 > seconds > chromium-63.0.3239.132: Fri Jan 19 06:11:06 2018: 1 hour, 16 minutes, 14 > seconds > chromium: 2 times >
There is a CPU-memory tradeoff here. Combining source files reduces duplication of #include directives which greatly cuts down on the number of lines of code going into the compiler, but the individual files being compiled are larger. I have a 12 SMT-core Ryzen 5-1600, and 16GB of RAM. I can't even build chromium on a tmpfs because the RAM+space requirements have grown, so I build on an SSD. Even without the tmpfs I have to reduce make to -j11 or it will OOM during a build WITHOUT the jumbo-build flag. So, I'm already hitting RAM limitations on build time. That said, I've experimented with some build times and I found that I can build chromium faster with -j8 using jumbo-build (the max # jobs I can run reliably without OOM) than I can build it with -j11 without using the new feature. I'll also note that to do this I have to make sure nothing else is compiling at the same time, and sometimes I end up stopping a container that runs mono for good measure. I do use ccache in general with chromium but I did my benchmarking without it. I suggest experimenting with jumbo-build, and consider reducing parallel jobs if you run into OOM, but depending on your system you might find it not worth the trouble. One thing I haven't experimented with is reducing -j even further and then moving back to a tmpfs. I could easily see a tmpfs for building outperforming jumbo-build even if I end up at -j4 or less. Then again, the SSD probably isn't as bad a drag as a spinning disk would be. I was chatting with somebody (I think on reddit) who mentioned jumbo-build worked fine on a threadripper with 64GB of RAM (that would be -j32 I suppose). I bet that with even a few more GB of RAM I could probably max out my 12 SMT cores. I can't wait to see how chromium-64 behaves. The RAM requirements have been steadily going up. I have an older system with only 4GB RAM and it struggles to even build chromium at all. -- Rich
