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

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Message-ID: <20170122044518.GB7057@tigerII.localdomain>
Date:   Sun, 22 Jan 2017 13:45:18 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     zhouxianrong <zhouxianrong@...wei.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        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@...wei.com,
        zhouxiyu@...wei.com, weidu.du@...wei.com, zhangshiming5@...wei.com,
        won.ho.park@...wei.com
Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram

On (01/22/17 10:58), zhouxianrong wrote:
> 1. memset is just set a int value but i want to set a long value.

ah... ok. because you union it with the handle.

> 2. using clear_page rather than memset MAYBE due to in arm64 arch
>    it is a 64-bytes operations.

clear_page() basically does memset(), which is quite well optimized.
except for arm64, yes.


> 6.6.4. Data Cache Zero
> 
> The ARMv8-A architecture introduces a Data Cache Zero by Virtual Address (DC ZVA) instruction. This enables a block of 64
> bytes in memory, aligned to 64 bytes in size, to be set to zero. If the DC ZVA instruction misses in the cache, it clears main
> memory, without causing an L1 or L2 cache allocation.
> 
> but i only consider the arm64 arch, other archs need to be reviewed.

thaks for the reply.

	-ss