linux-kernel - [RFC] background zero-set page for device

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Message-ID: <5493D9CE.5040001@lge.com>
Date:	Fri, 19 Dec 2014 16:54:54 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	이건호 <gunho.lee@....com>,
	Minchan Kim <minchan@...nel.org>,
	'김준수' <iamjoonsoo.kim@....com>
Subject: [RFC] background zero-set page for device

There was some discussion to create zero-set pages in background like this:
https://lkml.org/lkml/2004/10/30/73

I'm understand that it is not good for performance.

But I think it can help for a device in my platform.
I'm sorry I can't tell what it is.
But the device needs many zero-set pages, up to several MB,
so that device driver has a loop to calls alloc_page, memset(p, 0, PAGE_SIZE) and cache flush&invalidate.
And the device uses the pages and returns it to kernel. Kernel reads data in the page.

In this case, memset(0) must be done.
I think, if memset(0) is done at idle time, it can remove memset calling of ddk.

Is there any device that needs many zero-set pages?
Can backgound zero-setting page be good for the device?

-- 
Thanks,
Gioh Kim
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