Re: [PATCH] mm: refactor __vunmap() to avoid duplicated call to find_vm_area()
From: Roman Gushchin
Date: Wed May 15 2019 - 13:20:18 EST
On Wed, May 15, 2019 at 09:57:11AM +0530, Anshuman Khandual wrote:
> On 05/15/2019 05:21 AM, Roman Gushchin wrote:
> > __vunmap() calls find_vm_area() twice without an obvious reason:
> > first directly to get the area pointer, second indirectly by calling
> > vm_remove_mappings()->remove_vm_area(), which is again searching
> > for the area.
> > To remove this redundancy, let's split remove_vm_area() into
> > __remove_vm_area(struct vmap_area *), which performs the actual area
> > removal, and remove_vm_area(const void *addr) wrapper, which can
> > be used everywhere, where it has been used before. Let's pass
> > a pointer to the vm_area instead of vm_struct to vm_remove_mappings(),
> > so it can pass it to __remove_vm_area() and avoid the redundant area
> > lookup.
> > On my test setup, I've got 5-10% speed up on vfree()'ing 1000000
> > of 4-pages vmalloc blocks.
> Though results from 1000000 single page vmalloc blocks remain inconclusive,
> 4-page based vmalloc block's result shows improvement in the range of 5-10%.
So you can confirm my numbers? Great, thank you!