linux-kernel - [RFC] mm: why we should clear page when do anonymous page fault

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Message-ID: <56CA78F7.9010201@huawei.com>
Date:	Mon, 22 Feb 2016 10:56:55 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [RFC] mm: why we should clear page when do anonymous page fault

handle_pte_fault()
	do_anonymous_page()
		alloc_zeroed_user_highpage_movable()

We will alloc a zeroed page when do anonymous page fault, I don't know
why should clear it? just for safe?

If user space program do like the following, there are two memset 0, right?
kernel alloc zeroed page, and user memset 0 it again, this will waste a
lot of time.

main()
{
	...
	vaddr = malloc(size)
	if (vaddr)
		memset(vaddr, 0, size);
	...
}

Thanks,
Xishi Qiu