On 18/06/25 7:37 pm, Lorenzo Stoakes wrote:
On Wed, Jun 18, 2025 at 07:28:16PM +0530, Dev Jain wrote:
On 18/06/25 5:27 pm, Lorenzo Stoakes wrote:
On Wed, Jun 18, 2025 at 05:15:50PM +0530, Dev Jain wrote: Are you accounting for sys.max_map_count? If not, then you'll be hitting that first.
run_vmtests.sh will run the test in overcommit mode so that won't be an issue.
Umm, what? You mean overcommit all mode, and that has no bearing on the max mapping count check.
In do_mmap():
/* Too many mappings? */ if (mm->map_count > sysctl_max_map_count) return -ENOMEM;
As well as numerous other checks in mm/vma.c.
Ah sorry, didn't look at the code properly just assumed that overcommit_always meant overriding this.
I'm not sure why an overcommit toggle is even necessary when you could use MAP_NORESERVE or simply map PROT_NONE to avoid the OVERCOMMIT_GUESS limits?
I'm pretty confused as to what this test is really achieving honestly. This isn't a useful way of asserting mmap() behaviour as far as I can tell.
Well, seems like a useful way to me at least : ) Not sure if you are in the mood to discuss that but if you'd like me to explain from start to end what the test is doing, I can do that : )