It's not quite as radical as the jumbo build. As I recall, that tried to compile everything in one huge compilation. This meant it wasn't usable for regular development because a .cc file change would take 4 minutes.
In this case we are compiling up to 25 files at a time, and grouping them by directory. That means a .cc file change is still only about 30s, but the saving in total CPU time is not as dramatic. It also means you don't get conflicts between completely unrelated files, only the ones that are in the same directory. The 25-file limit is configurable in your 'gn gen' or your args.gn - if you have a very large or small number of cores you may want to adjust. I don't think github builders have a huge number of cores for example. Sadly your numbers show how much we have regressed. Neither the regular build, nor this cluster build are close to those numbers. I tried to get comparable numbers to your 8 year old test: * Building just d8 (not the tests) * -j8 * No ccache * Current origin/main * After ninja -t clean * Xeon (probably much faster than your CPU of 8 years ago) On Thu, Feb 26, 2026 at 10:03 AM Ben Noordhuis <[email protected]> wrote: > 1. V8, clean normal build, make -j8: 6:30m wall clock time, 47:48m cpu time Now half that speed on faster CPUS: 13m49s wall clock time, 104:51m cpu time > 2. V8, clean jumbo build, make -j1: 4:37m wall clock time, 4:34m cpu time I hadn't tried a j1 cluster build until now, but here it is: Sadly although the cpu time is 4x better than non-cluster build, it's 6x slower than the old jumbo build. Cluster size turned up to max: 24m40s wall clock time, 24m31s cpu time. For a somewhat more realistic modern developer experience, here's the -j16 time for the same workload, default cluster size: $ time ninja -j16 -C out.gn/x64.release d8 ninja: Entering directory `out.gn/x64.release' [2425/2425] LINK ./d8 real 2m21.231s user 33m45.009s sys 1m37.414s > > It was so much faster in human time and CPU time - staggeringly so in > the case of the latter. Granted, that was 8 year ago! > > [0] https://chromium-review.googlesource.com/c/v8/v8/+/1890090 > [1] https://github.com/nodejs/node/issues/18742 > > -- > -- > v8-dev mailing list > [email protected] > http://groups.google.com/group/v8-dev > --- > You received this message because you are subscribed to the Google Groups > "v8-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/v8-dev/CAHQurc_2dDruhqJG5RF1peNB9vVv9s5UuUwz9U_kVhnB5W-gtg%40mail.gmail.com. -- -- Erik Corry, working on V8 at Cloudflare -- -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/v8-dev/CAHZxHpgypyqG-Hmz%3DSU7feAkqHr-HWwS6FfgEn-ausna4KyKsw%40mail.gmail.com.
