linux-kernel - Re: [PATCH v2] arm64: mm: use macro instead of if judgement of ZONE

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Message-ID: <CAGZxSSSZ+b28rcHYRi5EWV9K4izHZBkO3fJTdang5XTaNMRTrw@mail.gmail.com>
Date:	Fri, 17 Oct 2014 11:08:43 +0800
From:	Yifan Zhang <yifan.zhangm@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Will Deacon <Will.Deacon@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"lauraa@...eaurora.org" <lauraa@...eaurora.org>,
	"ganapatrao.kulkarni@...iumnetworks.com" 
	<ganapatrao.kulkarni@...iumnetworks.com>,
	"robh@...nel.org" <robh@...nel.org>,
	"leif.lindholm@...aro.org" <leif.lindholm@...aro.org>,
	"Yalin.Wang@...ymobile.com" <Yalin.Wang@...ymobile.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yifan Zhang <zhangyf@...vell.com>
Subject: Re: [PATCH v2] arm64: mm: use macro instead of if judgement of ZONE_DMA

Hi Catalin,

I found In current arm64 code, there is no normal zone, only DMA zone.

Number of blocks type     Unmovable  Reclaimable      Movable
Reserve          CMA      Isolate

Node 0, zone    DMA          142           12           69
1           28            0


When zone_sizes_init, zone_size[ZONE_NORMAL] is initialized to 0. (it
is 3.10, I didn't try the latest code base)

static void __init zone_sizes_init(unsigned long min, unsigned long max)
{
    struct memblock_region *reg;
    unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
    unsigned long max_dma = min;

    memset(zone_size, 0, sizeof(zone_size));

#ifdef CONFIG_ZONE_DMA
    /* 4GB maximum for 32-bit only capable devices */
    unsigned long max_dma_phys =
        (unsigned long)(dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1);
    max_dma = max(min, min(max, max_dma_phys >> PAGE_SHIFT));
    zone_size[ZONE_DMA] = max_dma - min;
#endif
    zone_size[ZONE_NORMAL] = max - max_dma;


Then I just tried to enable ZONE_NORMAL in our platform, and found
this compiling error.

Is this ZONE_DMA cover full memory and ZONE_NORMAL = 0 strategy on
purpose ? We will not use ZONE_NORMAL on arm64 ?



On Fri, Oct 17, 2014 at 1:10 AM, Catalin Marinas
<catalin.marinas@....com> wrote:
> On Thu, Oct 16, 2014 at 10:41:01AM +0100, Yifan Zhang wrote:
>> if disable CONFIG_ZONE_DMA, ZONE_DMA becomes undefined.
>
> I agree that this is the case but can you explain why you need to
> disable ZONE_DMA? It currently is def_bool y, so it cannot be disabled
> unless you hack the Kconfig.
>
> --
> Catalin
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