From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1750842AbdAWEDh (ORCPT <rfc822;w@1wt.eu>);
        Sun, 22 Jan 2017 23:03:37 -0500
Received: from mail-pf0-f195.google.com ([209.85.192.195]:32838 "EHLO
        mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750711AbdAWEDf (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Sun, 22 Jan 2017 23:03:35 -0500
Date: Mon, 23 Jan 2017 13:03:47 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: zhouxianrong <zhouxianrong@huawei.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, sergey.senozhatsky@gmail.com,
        minchan@kernel.org, ngupta@vflare.org, Mi.Sophia.Wang@huawei.com,
        zhouxiyu@huawei.com, weidu.du@huawei.com, zhangshiming5@huawei.com,
        won.ho.park@huawei.com
Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram
Message-ID: <20170123040347.GA2327@jagdpanzerIV.localdomain>
References: <1483692145-75357-1-git-send-email-zhouxianrong@huawei.com>
 <1484296195-99771-1-git-send-email-zhouxianrong@huawei.com>
 <20170121084338.GA405@jagdpanzerIV.localdomain>
 <84073d07-6939-b22d-8bda-4fa2a9127555@huawei.com>
 <20170123025826.GA24581@js1304-P5Q-DELUXE>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170123025826.GA24581@js1304-P5Q-DELUXE>
User-Agent: Mutt/1.7.2 (2016-11-26)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On (01/23/17 11:58), Joonsoo Kim wrote:
> Hello,
> 
> 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.
> 
> Sorry for late review.
> 
> Do we really need to set a long value? I cannot believe that
> long value is repeated in the page. Value repeatition is
> usually done by value 0 or 1 and it's enough to use int. And, I heard
> that value 0 or 1 is repeated in Android. Could you check the distribution
> of the value in the same page?

Hello Joonsoo,

thanks for taking a look and for bringing this question up.
so I kinda wanted to propose union of `ulong handle' with `uint element'
and switching to memset(), but I couldn't figure out if that change would
break detection of some patterns.

 /* Allocated for each disk page */
 struct zram_table_entry {
-       unsigned long handle;
+       union {
+               unsigned long handle;
+               unsigned int element;
+       };
        unsigned long value;
 };

	-ss