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

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Date:	Wed, 9 Mar 2016 10:06:41 +0800
From:	Li Zhang <zhlcindy@...il.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	akpm@...ux-foundation.org, Vlastimil Babka <vbabka@...e.cz>,
	mgorman@...hsingularity.net,
	Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
	aneesh.kumar@...ux.vnet.ibm.com, 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

On Tue, Mar 8, 2016 at 5:36 PM, Michael Ellerman <mpe@...erman.id.au> wrote:
> 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%

Oh, sorry. It seems that I made a mistake.
>
> So you would say:
>
>   For 4GB of memory, boot time is improved by 59%, from 24.5s to 10s.

Got it. :)

>
>> 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
>



-- 

Best Regards
-Li