From: Peter Xu <peterx@redhat.com>
To: Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Huacai Chen <chenhuacai@kernel.org>,
David Hildenbrand <david@redhat.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Nathan Chancellor <nathan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
WANG Xuerui <kernel@xen0n.name>,
Ryan Roberts <ryan.roberts@arm.com>,
loongarch@lists.linux.dev
Subject: Re: [PATCH 1/3] mm: Allow anon exclusive check over hugetlb tail pages
Date: Thu, 4 Apr 2024 10:21:21 -0400 [thread overview]
Message-ID: <Zg63YZaXqYdSLHG-@x1n> (raw)
In-Reply-To: <Zg6z4ZEt7rbILgl8@casper.infradead.org>
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
next prev parent reply other threads:[~2024-04-04 14:21 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 1:32 [PATCH 0/3] mm/gup: fixups for hugetlb gup rework series peterx
2024-04-03 1:32 ` [PATCH 1/3] mm: Allow anon exclusive check over hugetlb tail pages peterx
2024-04-03 7:37 ` David Hildenbrand
2024-04-04 0:05 ` Matthew Wilcox
2024-04-04 13:45 ` Peter Xu
2024-04-04 14:06 ` Matthew Wilcox
2024-04-04 14:21 ` Peter Xu [this message]
2024-04-04 20:31 ` Andrew Morton
2024-04-04 20:36 ` Peter Xu
2024-04-03 1:32 ` [PATCH 2/3] fixup! mm/gup: handle huge pmd for follow_pmd_mask() peterx
2024-04-03 1:32 ` [PATCH 3/3] fixup! mm/arch: provide pud_pfn() fallback peterx
2024-04-03 11:06 ` [PATCH 0/3] mm/gup: fixups for hugetlb gup rework series Ryan Roberts
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