[PATCH v2 1/2] dma-direct: provide the ability to reserve per-numa CMA
From: Barry Song
Date: Thu Jun 25 2020 - 03:45:34 EST
This is useful for at least 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: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
---
include/linux/dma-contiguous.h | 4 ++
kernel/dma/Kconfig | 10 ++++
kernel/dma/contiguous.c | 99 ++++++++++++++++++++++++++++++----
3 files changed, 104 insertions(+), 9 deletions(-)
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 d006668c0027..aeb976b1d21c 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -104,6 +104,16 @@ 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 15bc5026c485..bcbd53aead93 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;
+static 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 +105,33 @@ 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;
+ char name[20];
+
+ snprintf(name, sizeof(name), "pernuma%d", nid);
+ ret = cma_declare_contiguous_nid(0, pernuma_size_bytes, 0, 0,
+ 0, false, name,
+ &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__,
+ (unsigned long long)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).
@@ -222,22 +258,31 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
* @gfp: Allocation flags.
*
* This function allocates contiguous memory buffer for specified device. It
- * tries to use device specific contiguous memory area if available, or the
- * default global one.
+ * tries to use device specific contiguous memory area if available, or it
+ * tries to use per-numa cma, if the allocation fails, it will fallback to
+ * try default global one.
*
- * 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
- * to waste CMA pages for that kind; it also helps reduce fragmentations.
+ * Note that it bypass one-page size of allocations from the per-numa and
+ * global area as the addresses within one page are always contiguous, so
+ * there is no need to waste CMA pages for that kind; it also helps reduce
+ * fragmentations.
*/
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 ? dev_to_node(dev) : NUMA_NO_NODE;
+ bool alloc_from_pernuma = false;
if (dev && dev->cma_area)
cma = dev->cma_area;
- else if (count > 1)
+ else if ((nid != NUMA_NO_NODE) && dma_contiguous_pernuma_area[nid]
+ && !(gfp & (GFP_DMA | GFP_DMA32))
+ && (count > 1)) {
+ cma = dma_contiguous_pernuma_area[nid];
+ alloc_from_pernuma = true;
+ } else if (count > 1)
cma = dma_contiguous_default_area;
/* CMA can be used only in the context which permits sleeping */
@@ -246,6 +291,11 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
+
+ /* fall back to default cma if failed in per-numa cma */
+ if (!page && alloc_from_pernuma)
+ page = cma_alloc(dma_contiguous_default_area, count,
+ cma_align, gfp & __GFP_NOWARN);
}
return page;
@@ -264,9 +314,40 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
*/
void dma_free_contiguous(struct device *dev, struct page *page, size_t size)
{
- if (!cma_release(dev_get_cma_area(dev), page,
- PAGE_ALIGN(size) >> PAGE_SHIFT))
- __free_pages(page, get_order(size));
+ /* if dev has its own cma, free page from there */
+ if (dev && dev->cma_area) {
+ if (cma_release(dev->cma_area, page, PAGE_ALIGN(size) >> PAGE_SHIFT))
+ return;
+ } else {
+ /*
+ * otherwise, page is from either per-numa cma or default cma
+ */
+ int nid = dev ? dev_to_node(dev) : NUMA_NO_NODE;
+
+ if (nid != NUMA_NO_NODE) {
+ int i;
+
+ /*
+ * Literally we only need to call cma_release() on pernuma cma of
+ * node nid, howerver, a corner case is that users might write
+ * /sys/devices/pci-x/numa_node to change node to workaround firmware
+ * bug, so it might allocate memory from nodeA CMA, but free from nodeB
+ * CMA.
+ */
+ for (i = 0; i < MAX_NUMNODES; i++) {
+ if (cma_release(dma_contiguous_pernuma_area[i], page,
+ PAGE_ALIGN(size) >> PAGE_SHIFT))
+ return;
+ }
+ }
+
+ if (cma_release(dma_contiguous_default_area, page,
+ PAGE_ALIGN(size) >> PAGE_SHIFT))
+ return;
+ }
+
+ /* not in any cma, free from buddy */
+ __free_pages(page, get_order(size));
}
/*
--
2.27.0