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staging: vchiq_arm: Usa a DMA pool for small bulks

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During a bulk transfer we request a DMA allocation to hold the
scatter-gather list.  Most of the time, this allocation is small
(<< PAGE_SIZE), however it can be requested at a high enough frequency
to cause fragmentation and/or stress the CMA allocator (think time
spent in compaction here, or during allocations elsewhere).

Implement a pool to serve up small DMA allocations, falling back
to a coherent allocation if the request is greater than
VCHIQ_DMA_POOL_SIZE.

Signed-off-by: Oliver Gjoneski <ogjoneski@gmail.com>
This commit is contained in:
detule
2018-10-02 04:10:08 -04:00
committed by Dom Cobley
parent 4b6b5ed198
commit cb18ce1e3b
1 changed files with 29 additions and 4 deletions
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33
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
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@@ -22,6 +22,7 @@
#include <linux/platform_device.h>
#include <linux/compat.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/rcupdate.h>
#include <linux/delay.h>
#include <linux/slab.h>
@@ -51,6 +52,8 @@
#define ARM_DS_ACTIVE BIT(2)
#define VCHIQ_DMA_POOL_SIZE PAGE_SIZE
/* Override the default prefix, which would be vchiq_arm (from the filename) */
#undef MODULE_PARAM_PREFIX
#define MODULE_PARAM_PREFIX DEVICE_NAME "."
@@ -133,6 +136,7 @@ struct vchiq_pagelist_info {
struct pagelist *pagelist;
size_t pagelist_buffer_size;
dma_addr_t dma_addr;
bool is_from_pool;
enum dma_data_direction dma_dir;
unsigned int num_pages;
unsigned int pages_need_release;
@@ -153,6 +157,7 @@ static void __iomem *g_regs;
* of 32.
*/
static unsigned int g_cache_line_size = 32;
static struct dma_pool *g_dma_pool;
static unsigned int g_use_36bit_addrs = 0;
static unsigned int g_fragments_size;
static char *g_fragments_base;
@@ -195,8 +200,13 @@ cleanup_pagelistinfo(struct vchiq_instance *instance, struct vchiq_pagelist_info
if (pagelistinfo->pages_need_release)
unpin_user_pages(pagelistinfo->pages, pagelistinfo->num_pages);
dma_free_coherent(instance->state->dev, pagelistinfo->pagelist_buffer_size,
pagelistinfo->pagelist, pagelistinfo->dma_addr);
if (pagelistinfo->is_from_pool) {
dma_pool_free(g_dma_pool, pagelistinfo->pagelist,
pagelistinfo->dma_addr);
} else {
dma_free_coherent(instance->state->dev, pagelistinfo->pagelist_buffer_size,
pagelistinfo->pagelist, pagelistinfo->dma_addr);
}
}
static inline bool
@@ -231,6 +241,7 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
u32 *addrs;
unsigned int num_pages, offset, i, k;
int actual_pages;
bool is_from_pool;
size_t pagelist_size;
struct scatterlist *scatterlist, *sg;
int dma_buffers;
@@ -260,8 +271,14 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
/* Allocate enough storage to hold the page pointers and the page
* list
*/
pagelist = dma_alloc_coherent(instance->state->dev, pagelist_size, &dma_addr,
GFP_KERNEL);
if (pagelist_size > VCHIQ_DMA_POOL_SIZE) {
pagelist = dma_alloc_coherent(instance->state->dev, pagelist_size, &dma_addr,
GFP_KERNEL);
is_from_pool = false;
} else {
pagelist = dma_pool_alloc(g_dma_pool, GFP_KERNEL, &dma_addr);
is_from_pool = true;
}
vchiq_log_trace(vchiq_arm_log_level, "%s - %pK", __func__, pagelist);
@@ -282,6 +299,7 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
pagelistinfo->pagelist = pagelist;
pagelistinfo->pagelist_buffer_size = pagelist_size;
pagelistinfo->dma_addr = dma_addr;
pagelistinfo->is_from_pool = is_from_pool;
pagelistinfo->dma_dir = (type == PAGELIST_WRITE) ?
DMA_TO_DEVICE : DMA_FROM_DEVICE;
pagelistinfo->num_pages = num_pages;
@@ -622,6 +640,13 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
}
g_dma_dev = dma_dev ?: dev;
g_dma_pool = dmam_pool_create("vchiq_scatter_pool", dev,
VCHIQ_DMA_POOL_SIZE, g_cache_line_size,
0);
if (!g_dma_pool) {
dev_err(dev, "failed to create dma pool");
return -ENOMEM;
}
vchiq_log_info(vchiq_arm_log_level, "vchiq_init - done (slots %pK, phys %pad)",
vchiq_slot_zero, &slot_phys);