Greetings, and thanks again for your report! While this issue was related to the strategy with which GCL seeks to use available memory, the issue also pertains to an anomaly in the algorithm the kernel uses to detect oom, hence the appearance only under particular combinations of ram and swap. Specifically, GCL probes brk at startup to see how much memory it can grab, and uniformly grows within this bound by a size-independent algorithm. If the fault purely lay with GCL, it should show up in all memory configurations. Instead, the kernel is denying a fork()/exec() required to run gcc externally in certain quasi-half-full situations but not others. The unpredictability mimics earlier problems on certain machines in which brk() would deliver the memory only for the kernel to give a segfault later when writes to it were attempted.
Now it is true that this fork()/exec() could be made more robust and oom-resistant by using posix_spawn() or equivalent procedure that does not attempt to copy the virtual memory image. Even though Linux is copy-on-write, the kernel page tables must still be copied, even though they will never be used if we immediately call exec(). But this only minimizes the issue. Better still would be to spawn a gcc-calling daemon early on with minimal memory footprint. Then one avoids spawning children as memory gets full. I may get around to this. For now I've put in a heuristic to try to match the heuristic used in the kernel. We default GCL_MEM_MULTIPLE to 0.85, which appears to always allow the fork()/exec() to run. This obviously is not optimal, but works for now. Take care, Santiago Vila <sanv...@unex.es> writes: >> * Bug fix: "FTBFS when built with dpkg-buildpackage -A (tests fail)", > > Thanks a lot. > > Perhaps I should have made a bug retitle because I suspect this did > not have anything to do with "dpkg-buildpackage -A" as such. > > You talked before in this bug about problems with garbage collection. > Would be possible for you to tell (briefly) what kind of problem this > was after all? > > And more importantly: After the fix, will it now work with 2GB of RAM > as well as 3GB or 4GB or any higher amount of memory? > > [ You will remember that the fact that it worked ok in your computer > and it did not in another one with more memory was the most annoying > thing about this bug ] > > > > -- Camm Maguire c...@maguirefamily.org ========================================================================== "The earth is but one country, and mankind its citizens." -- Baha'u'llah
