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authorBarry Song <song.bao.hua@hisilicon.com>2021-02-05 14:33:25 +0300
committerChristoph Hellwig <hch@lst.de>2021-02-05 14:48:46 +0300
commit9dc00b25eadf2908ae76ac0607b55a9f4e0e0cdc (patch)
tree3a80c0139e2eca5de2fd134189c26900dae9824c /kernel/dma
parent9f5f8ec50165630cfc49897410b30997d4d677b5 (diff)
downloadlinux-9dc00b25eadf2908ae76ac0607b55a9f4e0e0cdc.tar.xz
dma-mapping: benchmark: pretend DMA is transmitting
In a real dma mapping user case, after dma_map is done, data will be transmit. Thus, in multi-threaded user scenario, IOMMU contention should not be that severe. For example, if users enable multiple threads to send network packets through 1G/10G/100Gbps NIC, usually the steps will be: map -> transmission -> unmap. Transmission delay reduces the contention of IOMMU. Here a delay is added to simulate the transmission between map and unmap so that the tested result could be more accurate for TX and simple RX. A typical TX transmission for NIC would be like: map -> TX -> unmap since the socket buffers come from OS. Simple RX model eg. disk driver, is also map -> RX -> unmap, but real RX model in a NIC could be more complicated considering packets can come spontaneously and many drivers are using pre-mapped buffers pool. This is in the TBD list. Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma')
-rw-r--r--kernel/dma/map_benchmark.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
index da95df381483..e0e64f8b0739 100644
--- a/kernel/dma/map_benchmark.c
+++ b/kernel/dma/map_benchmark.c
@@ -21,6 +21,7 @@
#define DMA_MAP_BENCHMARK _IOWR('d', 1, struct map_benchmark)
#define DMA_MAP_MAX_THREADS 1024
#define DMA_MAP_MAX_SECONDS 300
+#define DMA_MAP_MAX_TRANS_DELAY (10 * NSEC_PER_MSEC)
#define DMA_MAP_BIDIRECTIONAL 0
#define DMA_MAP_TO_DEVICE 1
@@ -36,7 +37,8 @@ struct map_benchmark {
__s32 node; /* which numa node this benchmark will run on */
__u32 dma_bits; /* DMA addressing capability */
__u32 dma_dir; /* DMA data direction */
- __u8 expansion[84]; /* For future use */
+ __u32 dma_trans_ns; /* time for DMA transmission in ns */
+ __u8 expansion[80]; /* For future use */
};
struct map_benchmark_data {
@@ -87,6 +89,9 @@ static int map_benchmark_thread(void *data)
map_etime = ktime_get();
map_delta = ktime_sub(map_etime, map_stime);
+ /* Pretend DMA is transmitting */
+ ndelay(map->bparam.dma_trans_ns);
+
unmap_stime = ktime_get();
dma_unmap_single(map->dev, dma_addr, PAGE_SIZE, map->dir);
unmap_etime = ktime_get();
@@ -218,6 +223,11 @@ static long map_benchmark_ioctl(struct file *file, unsigned int cmd,
return -EINVAL;
}
+ if (map->bparam.dma_trans_ns > DMA_MAP_MAX_TRANS_DELAY) {
+ pr_err("invalid transmission delay\n");
+ return -EINVAL;
+ }
+
if (map->bparam.node != NUMA_NO_NODE &&
!node_possible(map->bparam.node)) {
pr_err("invalid numa node\n");