On 08/06/2017 05:05 PM, Daniel Santos wrote: > On 08/03/2017 11:45 AM, Jeff Law wrote: >> On 08/02/2017 11:34 PM, Daniel Santos wrote: >> So does this perform better than make -j X -l X? I use that with good >> success. >> >> jeff > > Sorry for my slow response! > > For a short answer, if you have 8 CPU cores and you run make -j8 -l8 > check then everything is fine until cron needs to do something that eats > 4 CPUs and you end up with a load average of 12. This is because the > make jobs of the test harness are very long running and make's only > control lever for regulating load is to not start new jobs until the > load falls. So if all jobs are already launched, make has no way of > reducing the load until all tests on that test set have completed. That's not something I typically see in practice. On my local machine I'm not usually awake when cron jobs are running, so if the load spikes due to over-subscription I don't much care :-)
The case that is of most interest to me is the effects on shared servers and folks that don't consistently use -l to throttle their jobs. Your patches would probably help in that situation by throttling parallelism independent of the -l flags. The second place where your stuff probably helps in a meaningful way is over-subscription due to parallelism within the gomp testsuite. I'll leave it to Mike who does most of the review work for the testing infrastructure these days. I won't objects on any philosophical grounds :-) Jeff