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From: John Stultz <john.stultz@linaro.org>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Amit Pundir <amit.pundir@linaro.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Will Deacon <will@kernel.org>,
	mbrugger@suse.com, Marc Zyngier <marc.zyngier@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	linux-mm <linux-mm@kvack.org>, Rob Herring <robh+dt@kernel.org>,
	wahrenst@gmx.net, Nicolas Dechense <nicolas.dechesne@linaro.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linux-rpi-kernel@lists.infradead.org
Subject: Re: [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32
Date: Mon, 2 Dec 2019 22:03:17 -0800
Message-ID: <CALAqxLW7RTif_NPxFXnxfTm2_ST+6aNmE6X=3v4XsuojKH2mtg@mail.gmail.com> (raw)
In-Reply-To: <CALAqxLUkPNf9JYyt+_VOrxq=Zq03veb1y-7aDx+_Vw+fF9i82A@mail.gmail.com>

On Mon, Dec 2, 2019 at 9:38 PM John Stultz <john.stultz@linaro.org> wrote:
> On Mon, Dec 2, 2019 at 9:08 PM John Stultz <john.stultz@linaro.org> wrote:
> > Hey Nicolas,
> >   Testing the db845c with linus/master, I found a regression causing
> > system hangs in early boot:
...
> > In the above log:
> > [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: -188245
> > looks the most suspect, and going back to the working a573cdd7973d +
> > build fix I see:
> > [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 957419
> >
> > Do you have any suggestions for what might be going wrong?
>
> Digging further, it seems the error is found in calculate_node_totalpages()
>  real_size = size - zone_absent_pages_in_node(pgdat->node_id, i,
>                                                   node_start_pfn, node_end_pfn,
>                                                   zholes_size);
>
> Where for zone DMA32 size is 262144, but real_size is calculated as -883520.
>
> I've not traced through to figure out why zone_absent_pages_in_node is
> coming up with such a large number yet, but I'm about to crash so I
> wanted to share.

Ok, narrowing it down further, it seems its the following bit from the patch:

> @@ -201,13 +212,18 @@ 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_dma32 = min;
> +       unsigned long max_dma = min;
>
>         memset(zone_size, 0, sizeof(zone_size));
>
> -       /* 4GB maximum for 32-bit only capable devices */
> +#ifdef CONFIG_ZONE_DMA
> +       max_dma = PFN_DOWN(arm64_dma_phys_limit);
> +       zone_size[ZONE_DMA] = max_dma - min;
> +       max_dma32 = max_dma;
> +#endif
>  #ifdef CONFIG_ZONE_DMA32
>         max_dma32 = PFN_DOWN(arm64_dma32_phys_limit);
> -       zone_size[ZONE_DMA32] = max_dma32 - min;
> +       zone_size[ZONE_DMA32] = max_dma32 - max_dma;
>  #endif
>         zone_size[ZONE_NORMAL] = max - max_dma32;
>
> @@ -219,11 +235,17 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>
>                 if (start >= max)
>                         continue;
> -
> +#ifdef CONFIG_ZONE_DMA
> +               if (start < max_dma) {
> +                       unsigned long dma_end = min_not_zero(end, max_dma);
> +                       zhole_size[ZONE_DMA] -= dma_end - start;
> +               }
> +#endif
>  #ifdef CONFIG_ZONE_DMA32
>                 if (start < max_dma32) {
> -                       unsigned long dma_end = min(end, max_dma32);
> -                       zhole_size[ZONE_DMA32] -= dma_end - start;
> +                       unsigned long dma32_end = min(end, max_dma32);
> +                       unsigned long dma32_start = max(start, max_dma);
> +                       zhole_size[ZONE_DMA32] -= dma32_end - dma32_start;
>                 }
>  #endif
>                 if (end > max_dma32) {

The zhole_sizes end up being:
zhole_size: DMA: 67671, DMA32: 1145664 NORMAL: 0

This seems to be due to dma32_start being calculated as 786432 each
time - I'm guessing that's the max_dma value.
Where dma32_end is around 548800, but changes each iteration (so we
end up subtracting a negative value each pass, growing the size).

thanks
-john

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  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11 18:25 [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 1/4] arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 2/4] arm64: rename variables used to calculate ZONE_DMA32's size Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32 Nicolas Saenz Julienne
2019-10-21 14:15   ` Qian Cai
2019-10-21 14:34     ` Nicolas Saenz Julienne
2019-10-21 14:46       ` Qian Cai
2019-10-21 17:01         ` Nicolas Saenz Julienne
2019-10-21 17:25           ` Qian Cai
2019-10-21 17:55             ` Nicolas Saenz Julienne
2019-10-21 20:36               ` Qian Cai
2019-10-22 11:23                 ` Nicolas Saenz Julienne
2019-10-23  7:11                   ` Matthias Brugger
2019-10-31 15:51                   ` Catalin Marinas
2019-10-31 16:04                     ` Nicolas Saenz Julienne
2019-10-31 18:02                       ` Catalin Marinas
2019-10-31 18:11                         ` Nicolas Saenz Julienne
2019-10-31 18:13                           ` Catalin Marinas
2019-12-03  5:08   ` John Stultz
2019-12-03  5:38     ` John Stultz
2019-12-03  6:03       ` John Stultz [this message]
2019-12-03 10:12         ` Will Deacon
2019-12-03 11:19           ` Catalin Marinas
2019-09-11 18:25 ` [PATCH v6 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Nicolas Saenz Julienne
2019-10-01 16:05 ` [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Catalin Marinas

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