On Wed, Jun 18, 2025 at 05:15:50PM +0530, Dev Jain wrote: > > On 18/06/25 5:07 pm, Lorenzo Stoakes wrote: > > On Wed, Jun 18, 2025 at 04:58:56PM +0530, Dev Jain wrote: > > > MAP_CHUNK_SIZE was chosen randomly. Good to see it translates into > > > something logical : ) > > > > > > So I guess I am correct, if we can find two VMAs (except at the edge of > > > the high addr boundary) > > > with a gap of greater than MAP_CHUNK_SIZE then there is a bug in mmap(). > > No haha, not at all!! Firstly fixed addressed override a lot of this, > > secondly > > the 256 page gap (which is configurable btw) is only applicable for mappings > > below a stack (in stack grow down arch). > > Sorry, I was making that assertion w.r.t this specific selftest. What the test > is doing is exhausting VA space without passing a hint or MAP_FIXED. With this > context, where does this assertion fail? One of them will be if the stack > guard > gap is more than 256 pages.
Are you accounting for sys.max_map_count? If not, then you'll be hitting that first. > > Also, note that the test hasn't reported frequent failures post my change, so > in general settings, w.r.t this test, the assertion experimentally seems to > be true : ) I don't really have time to dig into the test in detail sorry too much else on at the moment. But it isn't a big problem even if it happened to turn out that this test isn't really testing quite what you expected :)
