linux-kernel - Re: [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE

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Date:   Mon, 21 Oct 2019 16:36:57 -0400
From:   Qian Cai <cai@....pw>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     f.fainelli@...il.com, mbrugger@...e.com, marc.zyngier@....com,
        catalin.marinas@....com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, Rob Herring <robh+dt@...nel.org>,
        linux-rpi-kernel@...ts.infradead.org, m.szyprowski@...sung.com,
        Robin Murphy <Robin.Murphy@....com>, phill@...pberrypi.org,
        will@...nel.org, Christoph Hellwig <hch@....de>,
        linux-arm-kernel@...ts.infradead.org, wahrenst@....net
Subject: Re: [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32



> On Oct 21, 2019, at 1:55 PM, Nicolas Saenz Julienne <nsaenzjulienne@...e.de> wrote:
> 
> On Mon, 2019-10-21 at 13:25 -0400, Qian Cai wrote:
>>> On Oct 21, 2019, at 1:01 PM, Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>>> wrote:
>>> 
>>> Could you enable CMA debugging to see if anything interesting comes out of
>>> it.
>> 
>> I did but nothing interesting came out. Did you use the same config I gave?
> 
> Yes, aside from enabling ZONE_DMA.
> 
>> Also, it has those cmdline.
>> 
>> page_poison=on page_owner=on numa_balancing=enable \
>> systemd.unified_cgroup_hierarchy=1 debug_guardpage_minorder=1 \
>> page_alloc.shuffle=1
> 
> No luck, still works for me even after adding those extra flags. IIRC most of
> them (if not all) are not even parsed by the time CMA is configured.
> 
> So, can you confirm the zones setup you're seeing is similar to this one:
> 
> [    0.000000][    T0] Zone ranges:
> [    0.000000][    T0]   DMA      [mem 0x00000000802f0000-0x00000000bfffffff]
> [    0.000000][    T0]   DMA32    [mem 0x00000000c0000000-0x00000000ffffffff]
> [    0.000000][    T0]   Normal   [mem 0x0000000100000000-0x00000093fcffffff]
> 
> Maybe your memory starts between 0xe0000000-0xffffffff. That would be
> problematic (although somewhat unwarranted).

I managed to get more information here,

[    0.000000] cma: dma_contiguous_reserve(limit c0000000)
[    0.000000] cma: dma_contiguous_reserve: reserving 64 MiB for global area
[    0.000000] cma: cma_declare_contiguous(size 0x0000000004000000, base 0x0000000000000000, limit 0x00000000c0000000 alignment 0x0000000000000000)
[    0.000000] cma: Failed to reserve 512 MiB

Full dmesg:

https://cailca.github.io/files/dmesg.txt