From 9dc00b25eadf2908ae76ac0607b55a9f4e0e0cdc Mon Sep 17 00:00:00 2001 From: Barry Song Date: Sat, 6 Feb 2021 00:33:25 +1300 Subject: 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 Signed-off-by: Christoph Hellwig --- tools/testing/selftests/dma/dma_map_benchmark.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'tools') diff --git a/tools/testing/selftests/dma/dma_map_benchmark.c b/tools/testing/selftests/dma/dma_map_benchmark.c index 537d65968c48..fb23ce9617ea 100644 --- a/tools/testing/selftests/dma/dma_map_benchmark.c +++ b/tools/testing/selftests/dma/dma_map_benchmark.c @@ -12,9 +12,12 @@ #include #include +#define NSEC_PER_MSEC 1000000L + #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 +39,8 @@ 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 */ }; int main(int argc, char **argv) @@ -46,12 +50,12 @@ int main(int argc, char **argv) /* default single thread, run 20 seconds on NUMA_NO_NODE */ int threads = 1, seconds = 20, node = -1; /* default dma mask 32bit, bidirectional DMA */ - int bits = 32, dir = DMA_MAP_BIDIRECTIONAL; + int bits = 32, xdelay = 0, dir = DMA_MAP_BIDIRECTIONAL; int cmd = DMA_MAP_BENCHMARK; char *p; - while ((opt = getopt(argc, argv, "t:s:n:b:d:")) != -1) { + while ((opt = getopt(argc, argv, "t:s:n:b:d:x:")) != -1) { switch (opt) { case 't': threads = atoi(optarg); @@ -68,6 +72,9 @@ int main(int argc, char **argv) case 'd': dir = atoi(optarg); break; + case 'x': + xdelay = atoi(optarg); + break; default: return -1; } @@ -85,6 +92,12 @@ int main(int argc, char **argv) exit(1); } + if (xdelay < 0 || xdelay > DMA_MAP_MAX_TRANS_DELAY) { + fprintf(stderr, "invalid transmit delay, must be in 0-%ld\n", + DMA_MAP_MAX_TRANS_DELAY); + exit(1); + } + /* suppose the mininum DMA zone is 1MB in the world */ if (bits < 20 || bits > 64) { fprintf(stderr, "invalid dma mask bit, must be in 20-64\n"); @@ -109,6 +122,8 @@ int main(int argc, char **argv) map.node = node; map.dma_bits = bits; map.dma_dir = dir; + map.dma_trans_ns = xdelay; + if (ioctl(fd, cmd, &map)) { perror("ioctl"); exit(1); -- cgit v1.2.3