Nowadays, there are increasing requirements to benchmark the performance of dma_map and dma_unmap particually while the device is attached to an IOMMU.

This patch enables the support. Users can run specified number of threads to do dma_map_page and dma_unmap_page on a specific NUMA node with the specified duration. Then dma_map_benchmark will calculate the average latency for map and unmap.

A difficulity for this benchmark is that dma_map/unmap APIs must run on a particular device. Each device might have different backend of IOMMU or non-IOMMU.

So we use the driver_override to bind dma_map_benchmark to a particual device by: For platform devices: echo dma_map_benchmark > /sys/bus/platform/devices/xxx/driver_override echo xxx > /sys/bus/platform/drivers/xxx/unbind echo xxx > /sys/bus/platform/drivers/dma_map_benchmark/bind

For PCI devices: echo dma_map_benchmark > /sys/bus/pci/devices/0000:00:01.0/driver_override echo 0000:00:01.0 > /sys/bus/pci/drivers/xxx/unbind echo 0000:00:01.0 > /sys/bus/pci/drivers/dma_map_benchmark/bind

Cc: Joerg Roedel joro@8bytes.org Cc: Will Deacon will@kernel.org Cc: Shuah Khan shuah@kernel.org Cc: Christoph Hellwig hch@lst.de Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: Robin Murphy robin.murphy@arm.com Signed-off-by: Barry Song song.bao.hua@hisilicon.com --- -v2: * add PCI support; v1 supported platform devices only * replace ssleep by msleep_interruptible() to permit users to exit benchmark before it is completed * many changes according to Robin's suggestions, thanks! Robin - add standard deviation output to reflect the worst case - check users' parameters strictly like the number of threads - make cache dirty before dma_map - fix unpaired dma_map_page and dma_unmap_single; - remove redundant "long long" before ktime_to_ns(); - use devm_add_action(); - wakeup all threads together after they are ready

kernel/dma/Kconfig | 8 + kernel/dma/Makefile | 1 + kernel/dma/map_benchmark.c | 295 +++++++++++++++++++++++++++++++++++++ 3 files changed, 304 insertions(+) create mode 100644 kernel/dma/map_benchmark.c

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index c99de4a21458..949c53da5991 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -225,3 +225,11 @@ config DMA_API_DEBUG_SG is technically out-of-spec.

If unsure, say N. + +config DMA_MAP_BENCHMARK + bool "Enable benchmarking of streaming DMA mapping" + help + Provides /sys/kernel/debug/dma_map_benchmark that helps with testing + performance of dma_(un)map_page. + + See tools/testing/selftests/dma/dma_map_benchmark.c diff --git a/kernel/dma/Makefile b/kernel/dma/Makefile index dc755ab68aab..7aa6b26b1348 100644 --- a/kernel/dma/Makefile +++ b/kernel/dma/Makefile @@ -10,3 +10,4 @@ obj-$(CONFIG_DMA_API_DEBUG) += debug.o obj-$(CONFIG_SWIOTLB) += swiotlb.o obj-$(CONFIG_DMA_COHERENT_POOL) += pool.o obj-$(CONFIG_DMA_REMAP) += remap.o +obj-$(CONFIG_DMA_MAP_BENCHMARK) += map_benchmark.o diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c new file mode 100644 index 000000000000..ac397758087b --- /dev/null +++ b/kernel/dma/map_benchmark.c @@ -0,0 +1,295 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2020 Hisilicon Limited. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/debugfs.h> +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/dma-mapping.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/module.h> +#include <linux/pci.h> +#include <linux/platform_device.h> +#include <linux/slab.h> +#include <linux/timekeeping.h> + +#define DMA_MAP_BENCHMARK _IOWR('d', 1, struct map_benchmark) +#define DMA_MAP_MAX_THREADS 1024 +#define DMA_MAP_MAX_SECONDS 300 + +struct map_benchmark { + __u64 avg_map_100ns; /* average map latency in 100ns */ + __u64 map_stddev; /* standard deviation of map latency */ + __u64 avg_unmap_100ns; /* as above */ + __u64 unmap_stddev; + __u32 threads; /* how many threads will do map/unmap in parallel */ + __u32 seconds; /* how long the test will last */ + int node; /* which numa node this benchmark will run on */ + __u64 expansion[10]; /* For future use */ +}; + +struct map_benchmark_data { + struct map_benchmark bparam; + struct device *dev; + struct dentry *debugfs; + atomic64_t sum_map_100ns; + atomic64_t sum_unmap_100ns; + atomic64_t sum_square_map; + atomic64_t sum_square_unmap; + atomic64_t loops; +}; + +static int map_benchmark_thread(void *data) +{ + void *buf; + dma_addr_t dma_addr; + struct map_benchmark_data *map = data; + int ret = 0; + + buf = (void *)__get_free_page(GFP_KERNEL); + if (!buf) + return -ENOMEM; + + while (!kthread_should_stop()) { + __u64 map_100ns, unmap_100ns, map_square, unmap_square; + ktime_t map_stime, map_etime, unmap_stime, unmap_etime; + + /* + * for a non-coherent device, if we don't stain them in the cache, + * this will give an underestimate of the real-world overhead of + * BIDIRECTIONAL or TO_DEVICE mappings + * 66 means evertything goes well! 66 is lucky. + */ + memset(buf, 0x66, PAGE_SIZE); + + map_stime = ktime_get(); + dma_addr = dma_map_single(map->dev, buf, PAGE_SIZE, DMA_BIDIRECTIONAL); + if (unlikely(dma_mapping_error(map->dev, dma_addr))) { + pr_err("dma_map_single failed on %s\n", dev_name(map->dev)); + ret = -ENOMEM; + goto out; + } + map_etime = ktime_get(); + + unmap_stime = ktime_get(); + dma_unmap_single(map->dev, dma_addr, PAGE_SIZE, DMA_BIDIRECTIONAL); + unmap_etime = ktime_get(); + + /* calculate sum and sum of squares */ + map_100ns = ktime_to_ns(ktime_sub(map_etime, map_stime)) / 100; + unmap_100ns = ktime_to_ns(ktime_sub(unmap_etime, unmap_stime)) / 100; + map_square = map_100ns * map_100ns; + unmap_square = unmap_100ns * unmap_100ns; + + atomic64_add(map_100ns, &map->sum_map_100ns); + atomic64_add(unmap_100ns, &map->sum_unmap_100ns); + atomic64_add(map_square, &map->sum_square_map); + atomic64_add(unmap_square, &map->sum_square_unmap); + atomic64_inc(&map->loops); + } + +out: + free_page((unsigned long)buf); + return ret; +} + +static int do_map_benchmark(struct map_benchmark_data *map) +{ + struct task_struct **tsk; + int threads = map->bparam.threads; + int node = map->bparam.node; + const cpumask_t *cpu_mask = cpumask_of_node(node); + __u64 loops; + int ret = 0; + int i; + + tsk = kmalloc_array(threads, sizeof(tsk), GFP_KERNEL); + if (!tsk) + return -ENOMEM; + + get_device(map->dev); + + for (i = 0; i < threads; i++) { + tsk[i] = kthread_create_on_node(map_benchmark_thread, map, + map->bparam.node, "dma-map-benchmark/%d", i); + if (IS_ERR(tsk[i])) { + pr_err("create dma_map thread failed\n"); + ret = PTR_ERR(tsk[i]); + goto out; + } + + if (node != NUMA_NO_NODE && node_online(node)) + kthread_bind_mask(tsk[i], cpu_mask); + } + + /* clear the old value in the previous benchmark */ + atomic64_set(&map->sum_map_100ns, 0); + atomic64_set(&map->sum_unmap_100ns, 0); + atomic64_set(&map->sum_square_map, 0); + atomic64_set(&map->sum_square_unmap, 0); + atomic64_set(&map->loops, 0); + + for (i = 0; i < threads; i++) + wake_up_process(tsk[i]); + + msleep_interruptible(map->bparam.seconds * 1000); + + /* wait for the completion of benchmark threads */ + for (i = 0; i < threads; i++) { + ret = kthread_stop(tsk[i]); + if (ret) + goto out; + } + + loops = atomic64_read(&map->loops); + if (likely(loops > 0)) { + __u64 map_variance, unmap_variance; + + /* average latency */ + map->bparam.avg_map_100ns = atomic64_read(&map->sum_map_100ns) / loops; + map->bparam.avg_unmap_100ns = atomic64_read(&map->sum_unmap_100ns) / loops; + + /* standard deviation of latency */ + map_variance = atomic64_read(&map->sum_square_map) / loops - + map->bparam.avg_map_100ns * map->bparam.avg_map_100ns; + unmap_variance = atomic64_read(&map->sum_square_unmap) / loops - + map->bparam.avg_unmap_100ns * map->bparam.avg_unmap_100ns; + map->bparam.map_stddev = int_sqrt64(map_variance); + map->bparam.unmap_stddev = int_sqrt64(unmap_variance); + } + +out: + put_device(map->dev); + kfree(tsk); + return ret; +} + +static long map_benchmark_ioctl(struct file *filep, unsigned int cmd, + unsigned long arg) +{ + struct map_benchmark_data *map = filep->private_data; + int ret; + + if (copy_from_user(&map->bparam, (void __user *)arg, sizeof(map->bparam))) + return -EFAULT; + + switch (cmd) { + case DMA_MAP_BENCHMARK: + if (map->bparam.threads == 0 || map->bparam.threads > DMA_MAP_MAX_THREADS) { + pr_err("invalid thread number\n"); + return -EINVAL; + } + if (map->bparam.seconds == 0 || map->bparam.seconds > DMA_MAP_MAX_SECONDS) { + pr_err("invalid duration seconds\n"); + return -EINVAL; + } + + ret = do_map_benchmark(map); + break; + default: + return -EINVAL; + } + + if (copy_to_user((void __user *)arg, &map->bparam, sizeof(map->bparam))) + return -EFAULT; + + return ret; +} + +static const struct file_operations map_benchmark_fops = { + .open = simple_open, + .unlocked_ioctl = map_benchmark_ioctl, +}; + +static void map_benchmark_remove_debugfs(void *data) +{ + struct map_benchmark_data *map = (struct map_benchmark_data *)data; + + debugfs_remove(map->debugfs); +} + +static int __map_benchmark_probe(struct device *dev) +{ + struct dentry *entry; + struct map_benchmark_data *map; + int ret; + + map = devm_kzalloc(dev, sizeof(*map), GFP_KERNEL); + if (!map) + return -ENOMEM; + map->dev = dev; + + ret = devm_add_action(dev, map_benchmark_remove_debugfs, map); + if (ret) { + pr_err("Can't add debugfs remove action\n"); + return ret; + } + + /* + * we only permit a device bound with this driver, 2nd probe + * will fail + */ + entry = debugfs_create_file("dma_map_benchmark", 0600, NULL, map, + &map_benchmark_fops); + if (IS_ERR(entry)) + return PTR_ERR(entry); + map->debugfs = entry; + + return 0; +} + +static int map_benchmark_platform_probe(struct platform_device *pdev) +{ + return __map_benchmark_probe(&pdev->dev); +} + +static struct platform_driver map_benchmark_platform_driver = { + .driver = { + .name = "dma_map_benchmark", + }, + .probe = map_benchmark_platform_probe, +}; + +static int map_benchmark_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) +{ + return __map_benchmark_probe(&pdev->dev); +} + +static struct pci_driver map_benchmark_pci_driver = { + .name = "dma_map_benchmark", + .probe = map_benchmark_pci_probe, +}; + +static int __init map_benchmark_init(void) +{ + int ret; + + ret = pci_register_driver(&map_benchmark_pci_driver); + if (ret) + return ret; + + ret = platform_driver_register(&map_benchmark_platform_driver); + if (ret) { + pci_unregister_driver(&map_benchmark_pci_driver); + return ret; + } + + return 0; +} + +static void __exit map_benchmark_cleanup(void) +{ + platform_driver_unregister(&map_benchmark_platform_driver); + pci_unregister_driver(&map_benchmark_pci_driver); +} + +module_init(map_benchmark_init); +module_exit(map_benchmark_cleanup); + +MODULE_AUTHOR("Barry Song song.bao.hua@hisilicon.com"); +MODULE_DESCRIPTION("dma_map benchmark driver"); +MODULE_LICENSE("GPL");