Hi again, On 2026-10-09 20:09, Aurelien Jarno wrote: > Hi Helmut, > > On 2026-10-04 19:04, Helmut Grohne wrote: > > Hi Aurelien, > > > > On Sun, Oct 04, 2026 at 12:31:06PM +0200, Aurelien Jarno wrote: > > > Thanks for providing guess-concurrency, it's a clear improvement over > > > the number of open-coded equivalents in many debian/rules file. > > > > Thank you! > > > > > That said, I have observed that MemAvailable is sometimes significantly > > > lower than expected on some build daemons. I have tracked that to the > > > use of tmpfs as the build directory (which by the way is the default in > > > sbuild): until the data is flushed to the swap, the corresponding memory > > > amount disappears from MemAvailable. This causes the number of jobs to > > > be reduced for no real reason (the memory is still be available for > > > build), especially for packages with big sources. > > > > > > Could you please consider using MemTotal instead? I think it represents > > > better the amount of memory a build daemon is able to use. > > > > I see where you are coming from. When designing it, I was considering > > that system services (and in case of building on a desktop or laptop) > > also user applications may consume RAM. Simply going from MemAvailable > > to MemTotal would degrade that use case. An earlier version did use > > MemTotal, so it is not clear cut to me just yet. > > > > It seems like we do want to use some amount of swap, but swapping out > > everything might be too much. Can we find a middle ground? > > > > How about using > > > > MemAvailable + min(SwapFree, (MemTotal - MemAvailable) / 2) > > > > as a better approximation? I recognize that this is not going all the > > way that you want to go. However, it would still consider min(SwapFree, > > MemTotal / 2) as a minimum even if MemAvailable would be fully consumed > > with tmpfs. On systems without swap, this would result in the same > > behavior as before the change. > > While that's definitely an improvement, it's only a small improvement. > For a typical buildd with 16GB of RAM, if a package consists in 1GB of > source files, requires 4GB of build-dependencies installed in a 1GB > chroot, this reduces the available memory size as guessed by > guess-concurrency from 16GB to 13GB instead of 16GB to 10GB.
The memory used by tmpfs, but not yet swapped, appears in "Shmem". Therefore how about using MemAvailable + min(SwapFree, Shmem) ? Regards Aurelien -- Aurelien Jarno GPG: 4096R/1DDD8C9B [email protected] http://aurel32.net
