On 28 November 2017 11:07:58 GMT+01:00, Raffaele Belardi <raffaele.bela...@st.com> wrote: >Raffaele Belardi wrote: >> Hi, >> >> rebuilding system and world with gcc-7.2.0 on a 6-core AMD CPU I have >the impression that >> most of the ebuilds limit parallel builds to 1, 2 or 3 threads. I'm >aware it is only an >> impression, I did not spend the night monitoring the process, but >nevertheless every time >> I checked the load was very low. >> >> Does anyone have real-world statistics of CPU usage based on gentoo >world build? > >I graphed the number of parallel ebuilds while doing an 'emerge -e' >world on a 4-core CPU, >the graph is attached. There is an initial peak of ebuilds but I assume >it is fake data >due to prints being delayed. Then there is a long interval during which >there are few (~2) >ebuilds running. This may be due to lack of data (~700Mb still had to >be downloaded when I >started the emerge) or due to dependencies. Then, after ~500 merged >packages, finally the >number of parallel ebuilds rises to something very close to the >requested 5. > >Note: the graph represents the number of parallel ebuilds in time, not >the number of >parallel jobs. The latter would be more interesting but requires a lot >more effort. > >Note also in the log near the seamonkey build that the load rises to 15 >jobs; I suppose >seamonkey and other two potentially massively parallel jobs started >with low parallelism, >fooling emerge into starting all three of them, but then each one >spawned the full -j5 >jobs requested by MAKEOPTS. There's little emerge can do in these cases >to maintain the >load-average. > >All of this just to convince myself that yes, it is worth it! > >raffaele > >Method: >The relevant part of the command line: ># "MAKEOPTS=-j5 EMERGE_DEFAULT_OPTS=--jobs 3 --load-average 5" emerge >-e world >on a 4 core CPU. >In the log I substituted a +1 for every 'Emerging' and -1 for every >'Installing', removed >the rest of the line, summed and graphed the result.
Add the load average part to the makeopts and make will keep the jobs down when load rises. -- Joost -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
