On Thu, Mar 11, 2021 at 07:57:12PM -0500, Zi Yan wrote:
From: Zi Yan ziy@nvidia.com
We do not have a direct user interface of splitting the compound page backing a THP
But we do. You expand it.
and there is no need unless we want to expose the THP implementation details to users. Make <debugfs>/split_huge_pages accept a new command to do that.
By writing "<pid>,<vaddr_start>,<vaddr_end>" to <debugfs>/split_huge_pages, THPs within the given virtual address range from the process with the given pid are split. It is used to test split_huge_page function. In addition, a selftest program is added to tools/testing/selftests/vm to utilize the interface by splitting PMD THPs and PTE-mapped THPs.
Okay, makes sense.
But it doesn't cover non-mapped THPs. tmpfs may have file backed by THP that mapped nowhere. Do we want to cover this case too?
Maybe have PID:<pid>,<vaddr_start>,<vaddr_end> and FILE:<path>,<off_start>,<off_end> ?