Re: [PATCH v6 1/2] dma-contiguous: provide the ability to reserve per-numa CMA
From: Will Deacon <will@kernel.org>
Date: 2020-08-21 08:47:32
Also in:
linux-iommu, lkml
On Fri, Aug 21, 2020 at 02:26:14PM +1200, Barry Song wrote:
quoted hunk ↗ jump to hunk
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index bdc1f33fd3d1..3f33b89aeab5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt@@ -599,6 +599,15 @@ altogether. For more information, see include/linux/dma-contiguous.h + pernuma_cma=nn[MG] + [ARM64,KNL] + Sets the size of kernel per-numa memory area for + contiguous memory allocations. A value of 0 disables + per-numa CMA altogether. DMA users on node nid will + first try to allocate buffer from the pernuma area + which is located in node nid, if the allocation fails, + they will fallback to the global default memory area.
What is the default behaviour if this option is not specified? Seems like that should be mentioned here.
quoted hunk ↗ jump to hunk
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 847a9d1fa634..db7a37ed35eb 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig@@ -118,6 +118,16 @@ config DMA_CMA If unsure, say "n". if DMA_CMA + +config DMA_PERNUMA_CMA + bool "Enable separate DMA Contiguous Memory Area for each NUMA Node"
I don't understand the need for this config option. If you have DMA_DMA and you have NUMA, why wouldn't you want this enabled?
quoted hunk ↗ jump to hunk
+ help + Enable this option to get pernuma CMA areas so that devices like + ARM64 SMMU can get local memory by DMA coherent APIs. + + You can set the size of pernuma CMA by specifying "pernuma_cma=size" + on the kernel's command line. + comment "Default contiguous memory area size:" config CMA_SIZE_MBYTESdiff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index cff7e60968b9..89b95f10e56d 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c@@ -69,6 +69,19 @@ static int __init early_cma(char *p) } early_param("cma", early_cma); +#ifdef CONFIG_DMA_PERNUMA_CMA + +static struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES]; +static phys_addr_t pernuma_size_bytes __initdata; + +static int __init early_pernuma_cma(char *p) +{ + pernuma_size_bytes = memparse(p, &p); + return 0; +} +early_param("pernuma_cma", early_pernuma_cma); +#endif + #ifdef CONFIG_CMA_SIZE_PERCENTAGE static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)@@ -96,6 +109,34 @@ static inline __maybe_unused phys_addr_t cma_early_percent_memory(void) #endif +#ifdef CONFIG_DMA_PERNUMA_CMA +void __init dma_pernuma_cma_reserve(void) +{ + int nid; + + if (!pernuma_size_bytes) + return;
If this is useful (I assume it is), then I think we should have a non-zero default value, a bit like normal CMA does via CMA_SIZE_MBYTES.
+ for_each_node_state(nid, N_ONLINE) {
for_each_online_node() {
+ int ret; + char name[20];
20? Ah, wait, this is copy-pasta from hugetlb_cma_reserve(). Can you factor out the common parts at all? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel