linux-kernel - Re: [PATCH 02/19] x86, mm: Use big page size for small memory range

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Message-ID: <CAE9FiQW6+sjwBH9Rx634d6FpyG7DV9RYVg3AJKK5tW5Aa-D+Qg@mail.gmail.com>
Date:	Mon, 22 Oct 2012 09:33:07 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Konrad Rzeszutek Wilk <konrad@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Tejun Heo <tj@...nel.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/19] x86, mm: Use big page size for small memory range

On Mon, Oct 22, 2012 at 7:21 AM, Konrad Rzeszutek Wilk
<konrad@...nel.org> wrote:
> On Thu, Oct 18, 2012 at 01:50:12PM -0700, Yinghai Lu wrote:
>> We could map small range in the middle of big range at first, so should use
>> big page size at first to avoid using small page size to break down page table.
>>
>> Only can set big page bit when that range has ram area around it.
>
> The code looks good.
>
> I would alter the description to say:
>
> (Describe the problem)
>
> "We are wasting entries in the page-table b/c are not taking advantage
> of the fact that adjoining ranges could be of the same type and
> coalescing them together. Instead we end up using the small size type."
>
> (Explain your patch).
>
> "We fix this by iterating over the ranges, detecting whether the
> ranges that are next to each other are of the same type - and if so
> set them to our type."

I think my commit change log is clear enough, and will not update it.
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