* [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed
@ 2023-10-06 15:32 Catalin Marinas
2023-10-06 16:25 ` Robin Murphy
2023-10-13 18:45 ` Catalin Marinas
0 siblings, 2 replies; 4+ messages in thread
From: Catalin Marinas @ 2023-10-06 15:32 UTC (permalink / raw)
To: linux-arm-kernel; +Cc: Ross Burton, Robin Murphy, Will Deacon
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.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Suggested-by: Ross Burton <ross.burton@arm.com>
Cc: Ross Burton <ross.burton@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/mm/init.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 8a0f8604348b..54ee1a4868c2 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -493,8 +493,16 @@ void __init mem_init(void)
{
bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
- if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
+ if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
+ /*
+ * If no bouncing needed for ZONE_DMA, reduce the swiotlb
+ * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
+ */
+ unsigned long size =
+ ALIGN(memblock_phys_mem_size(), SZ_1G) >> 10;
+ swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
swiotlb = true;
+ }
swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed
2023-10-06 15:32 [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed Catalin Marinas
@ 2023-10-06 16:25 ` Robin Murphy
2023-10-06 16:45 ` Catalin Marinas
2023-10-13 18:45 ` Catalin Marinas
1 sibling, 1 reply; 4+ messages in thread
From: Robin Murphy @ 2023-10-06 16:25 UTC (permalink / raw)
To: Catalin Marinas, linux-arm-kernel; +Cc: Ross Burton, Will Deacon
On 2023-10-06 16:32, Catalin Marinas wrote:
> 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.
>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Suggested-by: Ross Burton <ross.burton@arm.com>
> Cc: Ross Burton <ross.burton@arm.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Will Deacon <will@kernel.org>
> ---
> arch/arm64/mm/init.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 8a0f8604348b..54ee1a4868c2 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -493,8 +493,16 @@ void __init mem_init(void)
> {
> bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
>
> - if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
> + if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
> + /*
> + * If no bouncing needed for ZONE_DMA, reduce the swiotlb
> + * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
> + */
> + unsigned long size =
> + ALIGN(memblock_phys_mem_size(), SZ_1G) >> 10;
Hmm, I wondered if DIV_ROUND_UP(memblock_phys_mem_size(), 1024) might be
any easier, but by the time I've typed it out it's still just as long :)
Either way then,
Reviewed-by Robin Murphy <robin.murphy@arm.com>
> + swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
> swiotlb = true;
> + }
>
> swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
>
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed
2023-10-06 16:25 ` Robin Murphy
@ 2023-10-06 16:45 ` Catalin Marinas
0 siblings, 0 replies; 4+ messages in thread
From: Catalin Marinas @ 2023-10-06 16:45 UTC (permalink / raw)
To: Robin Murphy; +Cc: linux-arm-kernel, Ross Burton, Will Deacon
On Fri, Oct 06, 2023 at 05:25:03PM +0100, Robin Murphy wrote:
> On 2023-10-06 16:32, Catalin Marinas wrote:
> > 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.
> >
> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> > Suggested-by: Ross Burton <ross.burton@arm.com>
> > Cc: Ross Burton <ross.burton@arm.com>
> > Cc: Robin Murphy <robin.murphy@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > ---
> > arch/arm64/mm/init.c | 10 +++++++++-
> > 1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 8a0f8604348b..54ee1a4868c2 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -493,8 +493,16 @@ void __init mem_init(void)
> > {
> > bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
> > - if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
> > + if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
> > + /*
> > + * If no bouncing needed for ZONE_DMA, reduce the swiotlb
> > + * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
> > + */
> > + unsigned long size =
> > + ALIGN(memblock_phys_mem_size(), SZ_1G) >> 10;
>
> Hmm, I wondered if DIV_ROUND_UP(memblock_phys_mem_size(), 1024) might be any
> easier, but by the time I've typed it out it's still just as long :)
It's not the same result as it's rounded up to the nearest KB rather
than MB. But this may work as well. I just made up this number really.
--
Catalin
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed
2023-10-06 15:32 [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed Catalin Marinas
2023-10-06 16:25 ` Robin Murphy
@ 2023-10-13 18:45 ` Catalin Marinas
1 sibling, 0 replies; 4+ messages in thread
From: Catalin Marinas @ 2023-10-13 18:45 UTC (permalink / raw)
To: linux-arm-kernel, Catalin Marinas; +Cc: Will Deacon, Ross Burton, Robin Murphy
On Fri, 06 Oct 2023 16:32:52 +0100, Catalin Marinas wrote:
> 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.
>
> [...]
Applied to arm64 (for-next/misc), thanks!
Also changed the division to DIV_ROUND_UP() as per Robin's suggestion.
[1/1] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed
https://git.kernel.org/arm64/c/65033574ade9
--
Catalin
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-10-06 15:32 [PATCH] arm64: swiotlb: Reduce the default size if no ZONE_DMA bouncing needed Catalin Marinas
2023-10-06 16:25 ` Robin Murphy
2023-10-06 16:45 ` Catalin Marinas
2023-10-13 18:45 ` Catalin Marinas
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