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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>
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@ -21,6 +21,7 @@
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#define DMA_MAP_BENCHMARK _IOWR('d', 1, struct map_benchmark)
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#define DMA_MAP_MAX_THREADS 1024
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#define DMA_MAP_MAX_SECONDS 300
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#define DMA_MAP_MAX_TRANS_DELAY (10 * NSEC_PER_MSEC)
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#define DMA_MAP_BIDIRECTIONAL 0
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#define DMA_MAP_TO_DEVICE 1
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@ -36,7 +37,8 @@ struct map_benchmark {
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__s32 node; /* which numa node this benchmark will run on */
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__u32 dma_bits; /* DMA addressing capability */
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__u32 dma_dir; /* DMA data direction */
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__u8 expansion[84]; /* For future use */
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__u32 dma_trans_ns; /* time for DMA transmission in ns */
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__u8 expansion[80]; /* For future use */
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};
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struct map_benchmark_data {
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@ -87,6 +89,9 @@ static int map_benchmark_thread(void *data)
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map_etime = ktime_get();
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map_delta = ktime_sub(map_etime, map_stime);
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/* Pretend DMA is transmitting */
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ndelay(map->bparam.dma_trans_ns);
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unmap_stime = ktime_get();
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dma_unmap_single(map->dev, dma_addr, PAGE_SIZE, map->dir);
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unmap_etime = ktime_get();
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@ -218,6 +223,11 @@ static long map_benchmark_ioctl(struct file *file, unsigned int cmd,
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return -EINVAL;
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}
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if (map->bparam.dma_trans_ns > DMA_MAP_MAX_TRANS_DELAY) {
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pr_err("invalid transmission delay\n");
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return -EINVAL;
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}
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if (map->bparam.node != NUMA_NO_NODE &&
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!node_possible(map->bparam.node)) {
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pr_err("invalid numa node\n");
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@ -12,9 +12,12 @@
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#include <sys/mman.h>
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#include <linux/types.h>
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#define NSEC_PER_MSEC 1000000L
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#define DMA_MAP_BENCHMARK _IOWR('d', 1, struct map_benchmark)
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#define DMA_MAP_MAX_THREADS 1024
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#define DMA_MAP_MAX_SECONDS 300
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#define DMA_MAP_MAX_TRANS_DELAY (10 * NSEC_PER_MSEC)
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#define DMA_MAP_BIDIRECTIONAL 0
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#define DMA_MAP_TO_DEVICE 1
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@ -36,7 +39,8 @@ struct map_benchmark {
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__s32 node; /* which numa node this benchmark will run on */
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__u32 dma_bits; /* DMA addressing capability */
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__u32 dma_dir; /* DMA data direction */
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__u8 expansion[84]; /* For future use */
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__u32 dma_trans_ns; /* time for DMA transmission in ns */
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__u8 expansion[80]; /* For future use */
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};
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int main(int argc, char **argv)
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@ -46,12 +50,12 @@ int main(int argc, char **argv)
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/* default single thread, run 20 seconds on NUMA_NO_NODE */
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int threads = 1, seconds = 20, node = -1;
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/* default dma mask 32bit, bidirectional DMA */
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int bits = 32, dir = DMA_MAP_BIDIRECTIONAL;
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int bits = 32, xdelay = 0, dir = DMA_MAP_BIDIRECTIONAL;
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int cmd = DMA_MAP_BENCHMARK;
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char *p;
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while ((opt = getopt(argc, argv, "t:s:n:b:d:")) != -1) {
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while ((opt = getopt(argc, argv, "t:s:n:b:d:x:")) != -1) {
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switch (opt) {
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case 't':
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threads = atoi(optarg);
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@ -68,6 +72,9 @@ int main(int argc, char **argv)
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case 'd':
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dir = atoi(optarg);
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break;
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case 'x':
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xdelay = atoi(optarg);
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break;
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default:
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return -1;
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}
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@ -85,6 +92,12 @@ int main(int argc, char **argv)
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exit(1);
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}
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if (xdelay < 0 || xdelay > DMA_MAP_MAX_TRANS_DELAY) {
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fprintf(stderr, "invalid transmit delay, must be in 0-%ld\n",
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DMA_MAP_MAX_TRANS_DELAY);
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exit(1);
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}
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/* suppose the mininum DMA zone is 1MB in the world */
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if (bits < 20 || bits > 64) {
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fprintf(stderr, "invalid dma mask bit, must be in 20-64\n");
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@ -109,6 +122,8 @@ int main(int argc, char **argv)
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map.node = node;
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map.dma_bits = bits;
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map.dma_dir = dir;
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map.dma_trans_ns = xdelay;
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if (ioctl(fd, cmd, &map)) {
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perror("ioctl");
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exit(1);
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