MaskRay added a comment. In D75153#1942336 <https://reviews.llvm.org/D75153#1942336>, @aganea wrote:
> In D75153#1906580 <https://reviews.llvm.org/D75153#1906580>, @MaskRay wrote: > > > Does `taskset -c 0-3 lld -flavor ...` restrict the number of cores? > > > > cpu_set_t cpu; > > sched_getaffinity(0, sizeof(cpu), &cpu); > > CPU_COUNT(&cpu) > > > Thanks for raising this! This does not seem to work (I currently only have > WSL at hand, no real Linux machine). I don't think it worked before my patch. > The current code in LLVM is written such as: (//note the "if" statement//) > > #if defined(HAVE_SCHED_GETAFFINITY) && defined(HAVE_CPU_COUNT) > cpu_set_t Set; > if (sched_getaffinity(0, sizeof(Set), &Set)) > return CPU_COUNT(&Set); > #endif > > > > > [[ https://linux.die.net/man/2/sched_getaffinity | The doc ]] for > `sched_getaffinity` says: > > > > On success, sched_setaffinity() and sched_getaffinity() return 0. On error, > > -1 is returned, and errno is set appropriately. > > So it would always fall back to `std::thread::hardware_concurrency`, which > apparently does not always take affinity into account, according to > @respindola (please see rG8c0ff9508da5f02e8ce6580a126a2018c9bf702a > <https://reviews.llvm.org/rG8c0ff9508da5f02e8ce6580a126a2018c9bf702a>). > > I'll write a follow-up patch to test affinity on Linux and Windows. Created D78324 <https://reviews.llvm.org/D78324> to fix this pre-existing issue. I remember I saw a related bugs.llvm.org report yesterday but I can't find it now... Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D75153/new/ https://reviews.llvm.org/D75153 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
