From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Matthew Wilcox <willy@infradead.org>,
Mina Almasry <almasrymina@google.com>
Cc: netdev@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Simon Horman <horms@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Jakub Kicinski <kuba@kernel.org>,
David Miller <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
Linux Next Mailing List <linux-next@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH net-next v1] mm: fix build on powerpc with GCC 14
Date: Sat, 14 Sep 2024 08:50:46 +0200 [thread overview]
Message-ID: <30e8dee7-e98e-42cb-aab3-6b75f1a6316d@csgroup.eu> (raw)
In-Reply-To: <ZuSQ9BT9Vg7O2kXv@casper.infradead.org>
Hi,
Le 13/09/2024 à 21:22, Matthew Wilcox a écrit :
> On Fri, Sep 13, 2024 at 07:20:36PM +0000, Mina Almasry wrote:
>> +++ b/include/linux/page-flags.h
>> @@ -239,8 +239,8 @@ static inline unsigned long _compound_head(const struct page *page)
>> {
>> unsigned long head = READ_ONCE(page->compound_head);
>>
>> - if (unlikely(head & 1))
>> - return head - 1;
>> + if (unlikely(head & 1UL))
>> + return head & ~1UL;
>> return (unsigned long)page_fixed_fake_head(page);
>
> NAK, that pessimises compound_head().
>
Can you please give more details on what the difference is ?
I can't see what it pessimises. In both cases, you test if the value is
odd, when it is odd you make it even.
Christophe
next prev parent reply other threads:[~2024-09-14 6:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-13 19:20 [PATCH net-next v1] mm: fix build on powerpc with GCC 14 Mina Almasry
2024-09-13 19:22 ` Matthew Wilcox
2024-09-14 6:50 ` Christophe Leroy [this message]
2024-09-15 10:44 ` Matthew Wilcox
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