linux-kernel - 答复: [PATCH] mm: extend zero pages to same element pages for zram

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Date:   Mon, 23 Jan 2017 06:32:55 +0000
From:   zhouxianrong <zhouxianrong@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "ngupta@...are.org" <ngupta@...are.org>,
        Mi Sophia Wang <Mi.Sophia.Wang@...wei.com>,
        Zhouxiyu <zhouxiyu@...wei.com>,
        "Duwei (Device OS)" <weidu.du@...wei.com>,
        "Zhangshiming (Simon, Device OS)" <zhangshiming5@...wei.com>,
        Won Ho Park <won.ho.park@...wei.com>
Subject: 答复: [PATCH] mm: extend zero pages to same element pages for zram

Yes, memset's prototype is int but
the implement of arch is unsigned char; for example, in arm64

	.weak memset
ENTRY(__memset)
ENTRY(memset)
	mov	dst, dstin	/* Preserve return value.  */
	and	A_lw, val, #255
	orr	A_lw, A_lw, A_lw, lsl #8
	orr	A_lw, A_lw, A_lw, lsl #16
	orr	A_l, A_l, A_l, lsl #32

-----邮件原件-----
发件人: Matthew Wilcox [mailto:willy@...radead.org] 
发送时间: 2017年1月23日 14:26
收件人: zhouxianrong
抄送: Sergey Senozhatsky; linux-mm@...ck.org; linux-kernel@...r.kernel.org; akpm@...ux-foundation.org; sergey.senozhatsky@...il.com; minchan@...nel.org; ngupta@...are.org; Mi Sophia Wang; Zhouxiyu; Duwei (Device OS); Zhangshiming (Simon, Device OS); Won Ho Park
主题: Re: [PATCH] mm: extend zero pages to same element pages for zram

On Sun, Jan 22, 2017 at 10:58:38AM +0800, zhouxianrong wrote:
> 1. memset is just set a int value but i want to set a long value.

memset doesn't set an int value.

DESCRIPTION
       The  memset()  function  fills  the  first  n  bytes of the memory area
       pointed to by s with the constant byte c.

It sets a byte value.  K&R just happened to choose 'int' as the type to store that "unsigned char" in.  Probably for very good reasons which make absolutely no sense today.