From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Yinghai Lu <yinghai@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Shaohua Li <shaohua.li@intel.com>,
Yakui Zhao <yakui.zhao@intel.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
arm-kernel@lists.infradead.org, kgene.kim@samsung.com,
Mel Gorman <mel@csn.ul.ie>
Subject: Re: [RFC] Tight check of pfn_valid on sparsemem
Date: Tue, 13 Jul 2010 08:20:09 +0100 [thread overview]
Message-ID: <20100713072009.GA19839@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <AANLkTinVwmo5pemz86nXaQT3V_ujaPLOsyNeQIFhL0Vu@mail.gmail.com>
On Tue, Jul 13, 2010 at 03:04:00PM +0900, Minchan Kim wrote:
> > __get_user() works with TLB and page table, the vaddr is really mapped or not.
> > If you got SEGV, __get_user() returns -EFAULT. It works per page granule.
Not in kernel space. It works on 1MB sections there.
Testing whether a page is mapped by __get_user is a hugely expensive
way to test whether a PFN is valid. It'd be cheaper to use our
flatmem implementation of pfn_valid() instead.
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next prev parent reply other threads:[~2010-07-13 7:21 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-12 15:53 [RFC] Tight check of pfn_valid on sparsemem Minchan Kim
2010-07-12 23:59 ` Kukjin Kim
2010-07-13 3:19 ` KAMEZAWA Hiroyuki
2010-07-13 4:11 ` Minchan Kim
2010-07-13 4:23 ` KAMEZAWA Hiroyuki
2010-07-13 6:04 ` Minchan Kim
2010-07-13 6:40 ` KAMEZAWA Hiroyuki
2010-07-13 8:06 ` Minchan Kim
2010-07-13 8:03 ` KAMEZAWA Hiroyuki
2010-07-13 7:20 ` Russell King - ARM Linux [this message]
2010-07-13 7:34 ` KAMEZAWA Hiroyuki
2010-07-13 7:58 ` KAMEZAWA Hiroyuki
2010-07-13 8:02 ` KAMEZAWA Hiroyuki
2010-07-13 18:39 ` Russell King - ARM Linux
2010-07-13 20:46 ` Dave Hansen
2010-07-13 9:30 ` Johannes Weiner
2010-07-13 15:43 ` Minchan Kim
2010-07-13 16:35 ` Dave Hansen
2010-07-13 16:44 ` Minchan Kim
2010-07-14 0:23 ` KAMEZAWA Hiroyuki
2010-07-14 6:44 ` Minchan Kim
2010-07-14 7:10 ` KAMEZAWA Hiroyuki
2010-07-14 7:35 ` Minchan Kim
2010-07-14 7:39 ` KAMEZAWA Hiroyuki
2010-07-14 7:50 ` Kukjin Kim
2010-07-14 8:09 ` KAMEZAWA Hiroyuki
2010-07-13 9:37 ` Mel Gorman
2010-07-13 9:46 ` Russell King - ARM Linux
2010-07-13 10:00 ` Mel Gorman
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