linux-kernel - Re: [PATCH 2/2] powerpc/mm: Enable page parallel initialisation

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Message-ID: <1457429794.31524.1.camel@ellerman.id.au>
Date:	Tue, 08 Mar 2016 20:36:34 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Li Zhang <zhlcindy@...il.com>, akpm@...ux-foundation.org,
	vbabka@...e.cz, mgorman@...hsingularity.net,
	khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com
Cc:	linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	Li Zhang <zhlcindy@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] powerpc/mm: Enable page parallel initialisation

Hi Li,

On Tue, 2016-03-08 at 11:55 +0800, Li Zhang wrote:

> From: Li Zhang <zhlcindy@...ux.vnet.ibm.com>
>
> Parallel initialisation has been enabled for X86, boot time is
> improved greatly. On Power8, it is improved greatly for small
> memory. Here is the result from my test on Power8 platform:
>
> For 4GB memory: 57% is improved, boot time as the following:
> with patch: 10s, without patch: 24.5s

This isn't worded quite right, and the numbers are a bit off.

old = 24.5
new = 10

So the improvement is 14.5 (seconds).

That means the improvement (14.5) as a percentage of the original boot time is:

 = 14.5 / 24.5 * 100
 = 59.183673469387756
 = 59%

So you would say:

  For 4GB of memory, boot time is improved by 59%, from 24.5s to 10s.

> For 50GB memory: 22% is improved, boot time as the following:
> with patch: 43.8s, without patch: 56.8s

  For 50GB memory, boot time is improved by 22%, from 56.8s to 43.8s.

> Acked-by: Mel Gorman <mgorman@...hsingularity.net>
> Signed-off-by: Li Zhang <zhlcindy@...ux.vnet.ibm.com>
> ---
>  * Add boot time details in change log.
>  * Please apply this patch after [PATCH 1/2] mm: meminit: initialise
>     more memory for inode/dentry hash tables in early boot, because
>    [PATCH 1/2] is to fix a bug which can be reproduced on Power.

Given that, I think it would be best if Andrew merged both of these patches.
Because this patch is pretty trivial, whereas the patch to mm/ is less so.

Is that OK Andrew?

For this one:

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers