Re: [PATCH] mm: Always sanity check anon_vma first for per-vma locks

[Peter Xu]

On Thu, Apr 11, 2024 at 10:27:56PM +0100, Matthew Wilcox wrote:
> On Thu, Apr 11, 2024 at 05:12:02PM -0400, Peter Xu wrote:
> > The question is whether that's intended to make it as complicated.  For
> > example, why don't we check anon_vma for anonymous too later when prepare
> > anon_vma, however we do it late for file memory.  AFAICT there's nothing
> > special with file memory in this case.
> 
> Yes, it's absolutely intended.  If anything, anon memory is the special
> case that checks up-front.
> 
> Congratulations on adding additional instructions to the common case.
> I don't understand why you persist with your nonsense.  Please stop.

How many instructions it takes for a late RETRY for WRITEs to private file
mappings, fallback to mmap_sem?

Did you even finish reading the patch at all?

-- 
Peter Xu