On Fri, 9 Jun 2023, Josh Triplett wrote: > The default kernel configuration does not allow any huge page allocation > until after setting nr_hugepages or nr_overcommit_hugepages to a > non-zero value; without setting those, mmap attempts with MAP_HUGETLB > will always fail with -ENOMEM. nr_overcommit_hugepages allows userspace > to attempt to allocate huge pages at runtime, succeeding if the kernel > can find or assemble a free huge page. > > Provide a Kconfig option to make nr_overcommit_hugepages default to > unlimited, which permits userspace to always attempt huge page > allocation on a best-effort basis. This makes it easier and more > worthwhile for random applications and libraries to opportunistically > attempt MAP_HUGETLB allocations without special configuration. > > In particular, current versions of liburing with IORING_SETUP_NO_MMAP > attempt to allocate the rings in a huge page. This seems likely to lead > to more applications and libraries attempting to use huge pages. > > Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Why not do this in an initscript? Or, if absolutely necessary, a kernel command line parameter? A Kconfig option to set a default value to be ULONG_MAX seems strange if you can just write the value to procfs.
