From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-media@vger.kernel.org, linux-mm@kvack.org,
linaro-mm-sig@lists.linaro.org,
Kyungmin Park <kyungmin.park@samsung.com>,
Russell King <linux@arm.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Ankita Garg <ankita@in.ibm.com>,
Daniel Walker <dwalker@codeaurora.org>,
Mel Gorman <mel@csn.ul.ie>, Arnd Bergmann <arnd@arndb.de>,
Jesse Barker <jesse.barker@linaro.org>,
Jonathan Corbet <corbet@lwn.net>,
Shariq Hasnain <shariq.hasnain@linaro.org>,
Chunsang Jeong <chunsang.jeong@linaro.org>
Subject: Re: [PATCH 2/8] mm: alloc_contig_freed_pages() added
Date: Wed, 21 Sep 2011 07:07:36 -0700 [thread overview]
Message-ID: <1316614056.16137.278.camel@nimitz> (raw)
In-Reply-To: <op.v15tv0183l0zgt@mnazarewicz-glaptop>
On Wed, 2011-09-21 at 15:17 +0200, Michal Nazarewicz wrote:
> > This 'struct page *'++ stuff is OK, but only for small, aligned areas.
> > For at least some of the sparsemem modes (non-VMEMMAP), you could walk
> > off of the end of the section_mem_map[] when you cross a MAX_ORDER
> > boundary. I'd feel a little bit more comfortable if pfn_to_page() was
> > being done each time, or only occasionally when you cross a section
> > boundary.
>
> I'm fine with that. I've used pointer arithmetic for performance reasons
> but if that may potentially lead to bugs then obviously pfn_to_page()
> should be used
pfn_to_page() on x86 these days is usually:
#define __pfn_to_page(pfn) (vmemmap + (pfn))
Even for the non-vmemmap sparsemem it stays pretty quick because the
section array is in cache as you run through the loop.
There are ways to _minimize_ the number of pfn_to_page() calls by
checking when you cross a section boundary, or even at a
MAX_ORDER_NR_PAGES boundary. But, I don't think it's worth the trouble.
-- Dave
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next prev parent reply other threads:[~2011-09-21 14:08 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-19 14:27 [PATCHv15 0/8] Contiguous Memory Allocator Marek Szyprowski
2011-08-19 14:27 ` [PATCH 1/8] mm: move some functions from memory_hotplug.c to page_isolation.c Marek Szyprowski
2011-08-19 14:27 ` [PATCH 2/8] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-09-08 18:05 ` Dave Hansen
2011-09-21 13:17 ` Michal Nazarewicz
2011-09-21 14:07 ` Dave Hansen [this message]
2011-09-21 15:19 ` [PATCH 1/3] fixup! " Michal Nazarewicz
2011-09-21 15:45 ` Dave Hansen
2011-09-21 16:26 ` Michal Nazarewicz
2011-09-21 16:30 ` Dave Hansen
2011-08-19 14:27 ` [PATCH 3/8] mm: alloc_contig_range() added Marek Szyprowski
2011-08-19 14:27 ` [PATCH 4/8] mm: MIGRATE_CMA migration type added Marek Szyprowski
2011-08-19 14:27 ` [PATCH 5/8] mm: MIGRATE_CMA isolation functions added Marek Szyprowski
2011-08-19 14:27 ` [PATCH 6/8] drivers: add Contiguous Memory Allocator Marek Szyprowski
2011-08-19 14:27 ` [PATCH 7/8] ARM: integrate CMA with DMA-mapping subsystem Marek Szyprowski
2011-09-08 17:27 ` Mike Frysinger
2011-09-21 13:47 ` Marek Szyprowski
2011-08-19 14:27 ` [PATCH 8/8] ARM: S5PV210: example of CMA private area for FIMC device on Goni board Marek Szyprowski
-- strict thread matches above, loose matches on Subject: below --
2011-07-20 8:57 [PATCHv12 0/8] Contiguous Memory Allocator Marek Szyprowski
2011-07-20 8:57 ` [PATCH 2/8] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-07-05 7:41 [PATCHv11 0/8] Contiguous Memory Allocator Marek Szyprowski
2011-07-05 7:41 ` [PATCH 2/8] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-07-05 11:30 ` Arnd Bergmann
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