Re: [PATCH 1/3] mm: Allow anon exclusive check over hugetlb tail pages

[Peter Xu <peterx@redhat.com>]

On Thu, Apr 04, 2024 at 03:06:25PM +0100, Matthew Wilcox wrote:
> On Thu, Apr 04, 2024 at 09:45:58AM -0400, Peter Xu wrote:
> > On Thu, Apr 04, 2024 at 01:05:57AM +0100, Matthew Wilcox wrote:
> > > 	if (PageHuge(page))
> > > 		page = compound_head(page);
> > 
> > I would think PageHead() check would help us to avoid compound_head() on
> > heads, which should still be the majority cases iiuc (assuming page->flags
> > is already around in the cache anyway).  I've no strong opinion though, as
> > I can hardly tell a difference in reality.
> 
> compound_head() includes a check for PageHead().  Adding the check just
> makes things slower.

They check different fields (compound_head, offset 0x8 for the former).
Again I'm ok with either way to go and I don't expect measurable
difference.. so if you prefer this I'm happy with it too.

Andrew, could you help update with Matthew's fixup?  The comment is
definitely better than what I wrote in all cases.

Thanks,

-- 
Peter Xu