From: Matthew Wilcox <willy@infradead.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags
Date: Sun, 30 Aug 2020 11:18:23 +0100 [thread overview]
Message-ID: <20200830101823.GY14765@casper.infradead.org> (raw)
In-Reply-To: <01c846d4-2fe4-eeef-6c79-e71fda1f9a39@linux.alibaba.com>
On Sun, Aug 30, 2020 at 06:14:33PM +0800, Alex Shi wrote:
> +++ b/mm/page_alloc.c
> @@ -532,9 +536,18 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
> mask <<= bitidx;
> flags <<= bitidx;
>
> +#ifdef CONFIG_CPU_V6
> + byte = (unsigned long)READ_ONCE(bitmap[byte_bitidx]);
> +#else
> byte = READ_ONCE(bitmap[byte_bitidx]);
> +#endif
> for (;;) {
> +#ifdef CONFIG_CPU_V6
> + /* arm v6 has no cmpxchgb function, so still false sharing long word */
> + old_byte = cmpxchg((unsigned long*)&bitmap[byte_bitidx], byte, (byte & ~mask) | flags);
> +#else
> old_byte = cmpxchg(&bitmap[byte_bitidx], byte, (byte & ~mask) | flags);
> +#endif
Good grief, no. Either come up with an appropriate abstraction or
abandon this patch. We can't possibly put this kind of ifdef in the
memory allocator!
next prev parent reply other threads:[~2020-08-30 10:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 5:47 Alex Shi
2020-08-19 5:47 ` [PATCH v2 2/2] mm/pageblock: remove false sharing in pageblock_flags Alex Shi
2020-08-19 7:57 ` Anshuman Khandual
2020-08-19 8:09 ` Alex Shi
2020-08-19 8:13 ` David Hildenbrand
2020-08-19 8:36 ` Alex Shi
2020-08-19 16:50 ` Alexander Duyck
2020-08-30 10:00 ` Alex Shi
2020-08-30 20:32 ` Alexander Duyck
2020-09-03 5:35 ` Alex Shi
2020-09-01 17:04 ` Vlastimil Babka
2020-08-19 7:55 ` [PATCH v2 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Anshuman Khandual
2020-08-19 8:04 ` David Hildenbrand
2020-08-30 10:08 ` Alex Shi
2020-08-30 10:14 ` Alex Shi
2020-08-30 10:18 ` Matthew Wilcox [this message]
2020-08-31 8:40 ` Alex Shi
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