On Thu, 12 Jun 2014, Waiman Long wrote: > > > The vma_address() function which is used to compute the virtual address > > > within a VMA is used only by 2 files in the mm subsystem - rmap.c and > > > huge_memory.c. This function is defined in rmap.c and is inlined by > > > its callers there, but it is also declared as an external function. > > > > > > However, the __split_huge_page() function which calls vma_address() > > > in huge_memory.c is calling it as a real function call. This is not > > > as efficient as an inlined function. This patch moves the underlying > > > inlined __vma_address() function to internal.h to be shared by both > > > the rmap.c and huge_memory.c file. > > This increases huge_memory.o's text+data_bss by 311 bytes, which makes > > me suspect that it is a bad change due to its increase of kernel cache > > footprint. > > > > Perhaps we should be noinlining __vma_address()? > > On my test machine, I saw an increase of 144 bytes in the text segment > of huge_memory.o. The size in size is caused by an increase in the size > of the __split_huge_page function. When I remove the > > if (unlikely(is_vm_hugetlb_page(vma))) > pgoff = page->index << huge_page_order(page_hstate(page)); > > check, the increase in size drops down to 24 bytes. As a THP cannot be > a hugetlb page, there is no point in doing this check for a THP. I will > update the patch to pass in an additional argument to disable this > check for __split_huge_page. > I think we're seeking a reason or performance numbers that suggest __vma_address() being inline is appropriate and so far we lack any such evidence. Adding additional parameters to determine checks isn't going to change the fact that it increases text size needlessly. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>