From: Mike Rapoport <rppt@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
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Christopher Lameter <cl@linux.com>,
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Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
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"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
James Bottomley <jejb@linux.ibm.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Mark Rutland <mark.rutland@arm.com>,
Michal Hocko <mhocko@suse.com>,
Mike Rapoport <rppt@linux.ibm.com>,
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x86@kernel.org, kernel test robot <oliver.sang@intel.com>
Subject: Re: [PATCH] secretmem: optimize page_is_secretmem()
Date: Mon, 19 Apr 2021 21:24:30 +0300 [thread overview]
Message-ID: <YH3K3sBFbNFOxTV+@kernel.org> (raw)
In-Reply-To: <20210419122156.GZ2531743@casper.infradead.org>
On Mon, Apr 19, 2021 at 01:21:56PM +0100, Matthew Wilcox wrote:
> On Mon, Apr 19, 2021 at 02:56:17PM +0300, Mike Rapoport wrote:
>
> > > With that fixed, you'll have a head page that you can use for testing,
> > > which means you don't need to test PageCompound() (because you know the
> > > page isn't PageTail), you can just test PageHead().
> >
> > I can't say I follow you here. page_is_secretmem() is intended to be a
> > generic test, so I don't see how it will get PageHead() if it is called
> > from other places.
>
> static inline bool head_is_secretmem(struct page *head)
> {
> if (PageHead(head))
> return false;
> ...
> }
>
> static inline bool page_is_secretmem(struct page *page)
> {
> if (PageTail(page))
> return false;
> return head_is_secretmem(page);
> }
>
> (yes, calling it head is a misnomer, because it's not necessarily a head,
> it might be a base page, but until we have a name for pages which might
> be a head page or a base page, it'll have to do ...)
To me this looks less clean and readable and in the end we have an extra
check for PG_Head if that won't get optimized away.
Does not seem to me there would be a measurable difference, but if this is
important for future conversion to folio I don't mind using
{head,page}_is_secretmem.
--
Sincerely yours,
Mike.
prev parent reply other threads:[~2021-04-19 18:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 8:42 [PATCH] secretmem: optimize page_is_secretmem() Mike Rapoport
2021-04-19 9:15 ` David Hildenbrand
2021-04-19 9:36 ` Mike Rapoport
2021-04-19 9:38 ` David Hildenbrand
2021-04-19 9:40 ` David Hildenbrand
2021-04-19 10:14 ` Mike Rapoport
2021-04-19 10:21 ` David Hildenbrand
2021-04-19 11:43 ` Matthew Wilcox
2021-04-19 11:23 ` Matthew Wilcox
2021-04-19 11:56 ` Mike Rapoport
2021-04-19 12:21 ` Matthew Wilcox
2021-04-19 18:24 ` Mike Rapoport [this message]
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