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From: Wu Fengguang <fengguang.wu@intel.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Zheng, Shaohui" <shaohui.zheng@intel.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
	"y-goto@jp.fujitsu.com" <y-goto@jp.fujitsu.com>,
	Dave Hansen <haveblue@us.ibm.com>,
	"x86@kernel.org" <x86@kernel.org>
Subject: Re: [ RESEND PATCH v3] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel
Date: Thu, 14 Jan 2010 21:24:51 +0800	[thread overview]
Message-ID: <20100114132451.GA2546@localhost> (raw)
In-Reply-To: <20100112170433.394be31b.kamezawa.hiroyu@jp.fujitsu.com>

Kame,

On Tue, Jan 12, 2010 at 05:04:33PM +0900, KAMEZAWA Hiroyuki wrote:

> 3 points...
> 1. I think this patch cannot be compiled in archs other than x86. Right ?
>    IOW, please add static inline dummy...

Good catch!

> 2. pgdat->[start,end], totalram_pages etc...are updated at memory hotplug.
>    Please place the hook nearby them.

arch/x86/mm/init_64.c:arch_add_memory() updates max_pfn_mapped, in
this sense it's equally OK to update max_pfn/max_low_pfn etc before
the call to arch_add_memory() ;)

> 3. I recommend you yo use memory hotplug notifier.
>    If it's allowed, it will be cleaner.

Hmm, notifier is for _outsider_ subsystems. It smells a bit
overkill to do notifier _inside_ the hotplug code.

>    It seems there are no strict ordering to update parameters this patch touches.

I tend to agree. That said, it does help keep our mind straight if we do it
in some logical order: max_pfn => max_pfn_mapped => totalram_pages etc.

Thanks,
Fengguang

WARNING: multiple messages have this Message-ID (diff)
From: Wu Fengguang <fengguang.wu@intel.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Zheng, Shaohui" <shaohui.zheng@intel.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
	"y-goto@jp.fujitsu.com" <y-goto@jp.fujitsu.com>,
	Dave Hansen <haveblue@us.ibm.com>,
	"x86@kernel.org" <x86@kernel.org>
Subject: Re: [ RESEND PATCH v3] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel
Date: Thu, 14 Jan 2010 21:24:51 +0800	[thread overview]
Message-ID: <20100114132451.GA2546@localhost> (raw)
In-Reply-To: <20100112170433.394be31b.kamezawa.hiroyu@jp.fujitsu.com>

Kame,

On Tue, Jan 12, 2010 at 05:04:33PM +0900, KAMEZAWA Hiroyuki wrote:

> 3 points...
> 1. I think this patch cannot be compiled in archs other than x86. Right ?
>    IOW, please add static inline dummy...

Good catch!

> 2. pgdat->[start,end], totalram_pages etc...are updated at memory hotplug.
>    Please place the hook nearby them.

arch/x86/mm/init_64.c:arch_add_memory() updates max_pfn_mapped, in
this sense it's equally OK to update max_pfn/max_low_pfn etc before
the call to arch_add_memory() ;)

> 3. I recommend you yo use memory hotplug notifier.
>    If it's allowed, it will be cleaner.

Hmm, notifier is for _outsider_ subsystems. It smells a bit
overkill to do notifier _inside_ the hotplug code.

>    It seems there are no strict ordering to update parameters this patch touches.

I tend to agree. That said, it does help keep our mind straight if we do it
in some logical order: max_pfn => max_pfn_mapped => totalram_pages etc.

Thanks,
Fengguang

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  parent reply	other threads:[~2010-01-14 13:58 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-12  7:45 [ RESEND PATCH v3] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel Zheng, Shaohui
2010-01-12  8:04 ` KAMEZAWA Hiroyuki
2010-01-12  8:04   ` KAMEZAWA Hiroyuki
2010-01-12  8:57   ` Zheng, Shaohui
2010-01-12  8:57     ` Zheng, Shaohui
2010-01-12  8:57     ` KAMEZAWA Hiroyuki
2010-01-12  8:57       ` KAMEZAWA Hiroyuki
2010-01-12  9:05       ` Zheng, Shaohui
2010-01-12  9:05         ` Zheng, Shaohui
2010-01-12 13:17       ` Zheng, Shaohui
2010-01-12 13:17         ` Zheng, Shaohui
2010-01-14 13:24   ` Wu Fengguang [this message]
2010-01-14 13:24     ` Wu Fengguang
2010-01-14 14:08     ` Wu Fengguang
2010-01-14 14:08       ` Wu Fengguang

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