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With CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC enabled, the arm64 kernel still allocates the default SWIOTLB buffer (64MB) even if ZONE_DMA is disabled or all the RAM fits into this zone. However, this potentially wastes a non-negligible amount of memory on platforms with little RAM. Reduce the SWIOTLB size to 1MB per 1GB of RAM if only needed for kmalloc() buffer bouncing.
57 lines
1.8 KiB
Diff
57 lines
1.8 KiB
Diff
From 7648741002eeb851ceb394864253445b77ea3d25 Mon Sep 17 00:00:00 2001
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From: Catalin Marinas <catalin.marinas@arm.com>
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Date: Wed, 10 Apr 2024 08:25:37 -0400
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Subject: [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA
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bouncing needed
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With CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC enabled, the arm64 kernel still
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allocates the default SWIOTLB buffer (64MB) even if ZONE_DMA is disabled
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or all the RAM fits into this zone. However, this potentially wastes a
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non-negligible amount of memory on platforms with little RAM.
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Reduce the SWIOTLB size to 1MB per 1GB of RAM if only needed for
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kmalloc() buffer bouncing.
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Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Suggested-by: Ross Burton <ross.burton@arm.com>
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Cc: Ross Burton <ross.burton@arm.com>
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Cc: Will Deacon <will@kernel.org>
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Reviewed-by: Robin Murphy <robin.murphy@arm.com>
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---
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arch/arm64/mm/init.c | 11 ++++++++++-
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1 file changed, 10 insertions(+), 1 deletion(-)
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diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
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index 8a0f8604348b..8deec68028ac 100644
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--- a/arch/arm64/mm/init.c
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+++ b/arch/arm64/mm/init.c
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@@ -16,6 +16,7 @@
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#include <linux/nodemask.h>
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#include <linux/initrd.h>
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#include <linux/gfp.h>
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+#include <linux/math.h>
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#include <linux/memblock.h>
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#include <linux/sort.h>
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#include <linux/of.h>
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@@ -493,8 +494,16 @@ void __init mem_init(void)
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{
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bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
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- if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
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+ if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
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+ /*
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+ * If no bouncing needed for ZONE_DMA, reduce the swiotlb
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+ * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
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+ */
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+ unsigned long size =
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+ DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
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+ swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
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swiotlb = true;
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+ }
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swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
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--
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2.39.2
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