On 6/18/13 12:01 PM, Dirk Jagdmann wrote: >> How many processor cores does your machine have, and are they >> multi-threaded? >> >> I have a 4-dual-threaded-core machine (and a solid-state disk and a >> lot of memory), and "-j 8" seems to run the CPU at about 100%. I >> don't know whether "number of threads" would be a good default in all >> cases - what you really want is to keep cranking up the number of jobs >> until things don't get faster, but that's a pain - but, if it is a >> good default, then >> >> sysctl -n hw.logicalcpu >> >> would give cores*threads-per-core (tested on Snow Leopard, Lion, and >> Mountain Lion; the script doesn't work on Leopard, as the versions of >> at least some of the software won't configure and build, and I gave up >> trying to make them build). >> >> (I originally used -j 4, but then saw something about a multi-threaded >> version of the IBM System/360 Model 195 that noted that >> multi-threading can help deal with pipeline bubbles due to unpredicted >> or mispredicted branches, so I tried -j 8 and found the CPU was busier >> than with -j 4.) > > hmm, there are many points discussed here: > > - do we want to make a smart decision on the number of parallel make > jobs, possibly derived from the number of cores? > > My personal opinion is yes. On OsX using the sysctl mentioned by Guy is > probably a good starting point. Adding my own experience you'll want to > oversubscribe the number of jobs over the number of cores a little bit, > so that when jobs are waiting for I/O action another job can use the > free CPU. With my personal experience calculating something like "number > of cores"*1.5 seems reasonable, because if you're waiting for the long > lasting build job on your desktop computer, you want some "juice" left > over for web browsing, email reading or whatever. (This applies to all > modern operating system, Windows, Linux, OsX) > > - the other question is, which versions of OsX are we targetting for > developer support going forward. Personally I think no serious Wireshark > user will use an earlier version of OsX than 10.6, so we should be safe. > > (personal note, my old MacBook Pro has two cores and no hyper-thread, so > personally I'm fine with 3 make jobs [note that this was the default in > the OsX build script for a long time])
I'm using "make -j -l 2" (keep spawning jobs until the system load is "2") on the buildbots. After a bit of experimentation that seems to utilize available cores without overloading the system, particularly if you have multiple builds running. ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev@wireshark.org> Archives: http://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-requ...@wireshark.org?subject=unsubscribe
