> On Aug 25, 2023, at 19:18, Usama Arif <usama.arif@xxxxxxxxxxxxx> wrote: > > The new boot flow when it comes to initialization of gigantic pages > is as follows: > - At boot time, for a gigantic page during __alloc_bootmem_hugepage, > the region after the first struct page is marked as noinit. > - This results in only the first struct page to be > initialized in reserve_bootmem_region. As the tail struct pages are > not initialized at this point, there can be a significant saving > in boot time if HVO succeeds later on. > - Later on in the boot, HVO is attempted. If its successful, only the first > HUGETLB_VMEMMAP_RESERVE_SIZE / sizeof(struct page) - 1 tail struct pages > after the head struct page are initialized. If it is not successful, > then all of the tail struct pages are initialized. > > Signed-off-by: Usama Arif <usama.arif@xxxxxxxxxxxxx> This edition is simpler than before ever, thanks for your work. There is premise that other subsystems do not access vmemmap pages before the initialization of vmemmap pages associated withe HugeTLB pages allocated from bootmem for your optimization. However, IIUC, the compacting path could access arbitrary struct page when memory fails to be allocated via buddy allocator. So we should make sure that those struct pages are not referenced in this routine. And I know if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, it will encounter the same issue, but I don't find any code to prevent this from happening. I need more time to confirm this, if someone already knows, please let me know, thanks. So I think HugeTLB should adopt the similar way to prevent this. Thanks.
