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Date: Wed, 3 Jun 2020 14:42:29 +1200
From: Barry Song <song.bao.hua@...ilicon.com>
To: <hch@....de>, <m.szyprowski@...sung.com>, <robin.murphy@....com>,
<catalin.marinas@....com>
CC: <iommu@...ts.linux-foundation.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
<Jonathan.Cameron@...wei.com>, <john.garry@...wei.com>,
<prime.zeng@...ilicon.com>,
Barry Song <song.bao.hua@...ilicon.com>,
Will Deacon <will@...nel.org>
Subject: [PATCH 1/3] dma-direct: provide the ability to reserve per-numa CMA
This is useful for two scenarios:
1. ARM64 smmu will get memory from local numa node, it can save its
command queues and page tables locally. Tests show it can decrease
dma_unmap latency at lot. For example, without this patch, smmu on
node2 will get memory from node0 by calling dma_alloc_coherent(),
typically, it has to wait for more than 560ns for the completion of
CMD_SYNC in an empty command queue; with this patch, it needs 240ns
only.
2. when we set iommu passthrough, drivers will get memory from CMA,
local memory means much less latency.
Cc: Will Deacon <will@...nel.org>
Cc: Robin Murphy <robin.murphy@....com>
Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
---
include/linux/dma-contiguous.h | 4 ++++
kernel/dma/Kconfig | 10 +++++++++
kernel/dma/contiguous.c | 41 +++++++++++++++++++++++++++++++++-
3 files changed, 54 insertions(+), 1 deletion(-)
diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
index 03f8e98e3bcc..278a80a40456 100644
--- a/include/linux/dma-contiguous.h
+++ b/include/linux/dma-contiguous.h
@@ -79,6 +79,8 @@ static inline void dma_contiguous_set_default(struct cma *cma)
void dma_contiguous_reserve(phys_addr_t addr_limit);
+void dma_pernuma_cma_reserve(void);
+
int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
phys_addr_t limit, struct cma **res_cma,
bool fixed);
@@ -128,6 +130,8 @@ static inline void dma_contiguous_set_default(struct cma *cma) { }
static inline void dma_contiguous_reserve(phys_addr_t limit) { }
+static inline void dma_pernuma_cma_reserve(void) { }
+
static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
phys_addr_t limit, struct cma **res_cma,
bool fixed)
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 4c103a24e380..14f4a1fe4285 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -100,6 +100,16 @@ config DMA_CMA
if DMA_CMA
comment "Default contiguous memory area size:"
+config CMA_PERNUMA_SIZE_MBYTES
+ int "Size in Mega Bytes for per-numa CMA areas"
+ depends on NUMA
+ default 16 if ARM64
+ default 0
+ help
+ Defines the size (in MiB) of the per-numa memory area for Contiguous
+ Memory Allocator. Every numa node will get a separate CMA with this
+ size. If the size of 0 is selected, per-numa CMA is disabled.
+
config CMA_SIZE_MBYTES
int "Size in Mega Bytes"
depends on !CMA_SIZE_SEL_PERCENTAGE
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 8bc6f2d670f9..4b10d0ca0456 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -30,7 +30,14 @@
#define CMA_SIZE_MBYTES 0
#endif
+#ifdef CONFIG_CMA_PERNUMA_SIZE_MBYTES
+#define CMA_SIZE_PERNUMA_MBYTES CONFIG_CMA_PERNUMA_SIZE_MBYTES
+#else
+#define CMA_SIZE_PERNUMA_MBYTES 0
+#endif
+
struct cma *dma_contiguous_default_area;
+struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES];
/*
* Default global CMA area size can be defined in kernel's .config.
@@ -44,6 +51,8 @@ struct cma *dma_contiguous_default_area;
*/
static const phys_addr_t size_bytes __initconst =
(phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
+static const phys_addr_t pernuma_size_bytes __initconst =
+ (phys_addr_t)CMA_SIZE_PERNUMA_MBYTES * SZ_1M;
static phys_addr_t size_cmdline __initdata = -1;
static phys_addr_t base_cmdline __initdata;
static phys_addr_t limit_cmdline __initdata;
@@ -96,6 +105,31 @@ static inline __maybe_unused phys_addr_t cma_early_percent_memory(void)
#endif
+void __init dma_pernuma_cma_reserve(void)
+{
+ int nid;
+
+ if (!pernuma_size_bytes || nr_online_nodes <= 1)
+ return;
+
+ for_each_node_state(nid, N_ONLINE) {
+ int ret;
+
+ ret = cma_declare_contiguous_nid(0, pernuma_size_bytes, 0, 0,
+ 0, false, "pernuma",
+ &dma_contiguous_pernuma_area[nid],
+ nid);
+ if (ret) {
+ pr_warn("%s: reservation failed: err %d, node %d", __func__,
+ ret, nid);
+ continue;
+ }
+
+ pr_debug("%s: reserved %llu MiB on node %d\n", __func__,
+ pernuma_size_bytes / SZ_1M, nid);
+ }
+}
+
/**
* dma_contiguous_reserve() - reserve area(s) for contiguous memory handling
* @limit: End address of the reserved memory (optional, 0 for any).
@@ -223,7 +257,8 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
*
* This function allocates contiguous memory buffer for specified device. It
* first tries to use device specific contiguous memory area if available or
- * the default global one, then tries a fallback allocation of normal pages.
+ * the per-numa ones and default global one, then tries a fallback allocation
+ * of normal pages. per-numa memory areas don't support address limit
*
* Note that it byapss one-page size of allocations from the global area as
* the addresses within one page are always contiguous, so there is no need
@@ -234,9 +269,13 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
size_t count = size >> PAGE_SHIFT;
struct page *page = NULL;
struct cma *cma = NULL;
+ int nid = dev_to_node(dev);
if (dev && dev->cma_area)
cma = dev->cma_area;
+ else if ((nid != NUMA_NO_NODE) && dma_contiguous_pernuma_area[nid]
+ && !(gfp & (GFP_DMA | GFP_DMA32)))
+ cma = dma_contiguous_pernuma_area[nid];
else if (count > 1)
cma = dma_contiguous_default_area;
--
2.23.0
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