Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, Jun 06, 2018 at 08:55:15AM -0700, Nadav Amit wrote: >>> -#define LATENCY_LIMIT (64 * PAGE_SIZE) >>> +#define LATENCY_LIMIT (PMD_SIZE) >>> >>> unsigned long move_page_tables(struct vm_area_struct *vma, >>> unsigned long old_addr, struct vm_area_struct *new_vma, >> >> This LATENCY_LIMIT is only used in move_page_tables() in the following >> manner: >> >> next = (new_addr + PMD_SIZE) & PMD_MASK; >> if (extent > next - new_addr) >> extent = next - new_addr; >> if (extent > LATENCY_LIMIT) >> extent = LATENCY_LIMIT; >> >> If LATENCY_LIMIT is to be changed to PMD_SIZE, then IIUC the last condition >> is not required, and LATENCY_LIMIT can just be removed (assuming there is no >> underflow case that hides somewhere). > > I see no problem removing it other than we may forget that we ever limited > PTE lock hold times for any reason. I'm skeptical it will matter unless > mremap-intensive workloads are a lot more common than I believe. I have no opinion regarding the behavior change. It is just that code with no effect is oftentimes confusing. A comment (if needed) can replace the code, and git history would provide how it was once supported.
