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Message-ID: <CAGsJ_4xmC5wP9ut7X6cj72xq1qNGdVCC==8c9FQpd3SbCQ-iNw@mail.gmail.com>
Date: Fri, 9 May 2025 15:41:31 +1200
From: Barry Song <21cnbao@...il.com>
To: Qinxin Xia <xiaqinxin@...wei.com>, Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>
Cc: yangyicong@...wei.com, hch@....de, iommu@...ts.linux.dev,
jonathan.cameron@...wei.com, prime.zeng@...wei.com, fanghao11@...wei.com,
linux-kernel@...r.kernel.org, linuxarm@...wei.com
Subject: Re: [PATCH v3 2/4] dma-mapping: benchmark: modify the framework to
adapt to more map modes
On Fri, May 9, 2025 at 2:02 PM Qinxin Xia <xiaqinxin@...wei.com> wrote:
>
> In some service scenarios, the performance of dma_map_sg needs to be
> tested to support different map modes for benchmarks. This patch adjusts
> the DMA map benchmark framework to make the DMA map benchmark framework
> more flexible and adaptable to other mapping modes in the future.
> By abstracting the framework into four interfaces:prepare, unprepare,
> do_map, and do_unmap.The new map schema can be introduced more easily
> without major modifications to the existing code structure.
>
> Signed-off-by: Qinxin Xia <xiaqinxin@...wei.com>
- stable@...r.kernel.org
+ Marek
+ Robin,
Once the minor issues below are addressed, feel free to add:
Reviewed-by: Barry Song <baohua@...nel.org>
> ---
> include/linux/map_benchmark.h | 8 ++-
> kernel/dma/map_benchmark.c | 122 +++++++++++++++++++++++++++-------
> 2 files changed, 106 insertions(+), 24 deletions(-)
>
> diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
> index 2ac2fe52f248..5294dfd1870f 100644
> --- a/include/linux/map_benchmark.h
> +++ b/include/linux/map_benchmark.h
> @@ -15,6 +15,11 @@
> #define DMA_MAP_TO_DEVICE 1
> #define DMA_MAP_FROM_DEVICE 2
>
> +enum {
> + DMA_MAP_SINGLE_MODE,
> + DMA_MAP_MODE_MAX
> +};
Using a more specific namespace—such as DMA_MAP_BENCH_SINGLE_MODE
and DMA_MAP_BENCH_MODE_MAX—would help avoid potential naming
conflicts.
> +
> struct map_benchmark {
> __u64 avg_map_100ns; /* average map latency in 100ns */
> __u64 map_stddev; /* standard deviation of map latency */
> @@ -27,6 +32,7 @@ struct map_benchmark {
> __u32 dma_dir; /* DMA data direction */
> __u32 dma_trans_ns; /* time for DMA transmission in ns */
> __u32 granule; /* how many PAGE_SIZE will do map/unmap once a time */
> - __u8 expansion[76]; /* For future use */
> + __u8 map_mode; /* the mode of dma map */
> + __u8 expansion[75]; /* For future use */
> };
> #endif /* _KERNEL_DMA_BENCHMARK_H */
> diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
> index cc19a3efea89..47a06b891db8 100644
> --- a/kernel/dma/map_benchmark.c
> +++ b/kernel/dma/map_benchmark.c
> @@ -5,6 +5,7 @@
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> +#include <linux/cleanup.h>
> #include <linux/debugfs.h>
> #include <linux/delay.h>
> #include <linux/device.h>
> @@ -31,17 +32,99 @@ struct map_benchmark_data {
> atomic64_t loops;
> };
>
> +struct map_benchmark_ops {
> + void *(*prepare)(struct map_benchmark_data *map);
> + void (*unprepare)(void *mparam);
> + int (*do_map)(void *mparam);
> + void (*do_unmap)(void *mparam);
> +};
> +
> +struct dma_single_map_param {
> + struct device *dev;
> + dma_addr_t addr;
> + void *xbuf;
> + u32 npages;
> + u32 dma_dir;
> +};
> +
> +static void *dma_single_map_benchmark_prepare(struct map_benchmark_data *map)
> +{
> + struct dma_single_map_param *params __free(kfree) = kzalloc(sizeof(*params),
> + GFP_KERNEL);
> + if (!params)
> + return NULL;
> +
> + params->npages = map->bparam.granule;
> + params->dma_dir = map->bparam.dma_dir;
> + params->dev = map->dev;
> + params->xbuf = alloc_pages_exact(params->npages * PAGE_SIZE, GFP_KERNEL);
> + if (!params->xbuf)
> + return NULL;
> +
> + /*
> + * 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.
> + */
> + if (params->dma_dir != DMA_FROM_DEVICE)
> + memset(params->xbuf, 0x66, params->npages * PAGE_SIZE);
> +
> + return_ptr(params);
> +}
> +
> +static void dma_single_map_benchmark_unprepare(void *mparam)
> +{
> + struct dma_single_map_param *params = mparam;
> +
> + free_pages_exact(params->xbuf, params->npages * PAGE_SIZE);
> + kfree(params);
> +}
> +
> +static int dma_single_map_benchmark_do_map(void *mparam)
> +{
> + struct dma_single_map_param *params = mparam;
> + int ret = 0;
> +
> + params->addr = dma_map_single(params->dev, params->xbuf,
> + params->npages * PAGE_SIZE, params->dma_dir);
> + if (unlikely(dma_mapping_error(params->dev, params->addr))) {
> + pr_err("dma_map_single failed on %s\n", dev_name(params->dev));
> + ret = -ENOMEM;
> + }
> +
> + return ret;
> +}
> +
> +static void dma_single_map_benchmark_do_unmap(void *mparam)
> +{
> + struct dma_single_map_param *params = mparam;
> +
> + dma_unmap_single(params->dev, params->addr,
> + params->npages * PAGE_SIZE, params->dma_dir);
> +}
> +
> +static struct map_benchmark_ops dma_single_map_benchmark_ops = {
> + .prepare = dma_single_map_benchmark_prepare,
> + .unprepare = dma_single_map_benchmark_unprepare,
> + .do_map = dma_single_map_benchmark_do_map,
> + .do_unmap = dma_single_map_benchmark_do_unmap,
> +};
> +
> +static struct map_benchmark_ops *dma_map_benchmark_ops[DMA_MAP_MODE_MAX] = {
> + [DMA_MAP_SINGLE_MODE] = &dma_single_map_benchmark_ops,
> +};
> +
> static int map_benchmark_thread(void *data)
> {
> - void *buf;
> - dma_addr_t dma_addr;
> struct map_benchmark_data *map = data;
> - int npages = map->bparam.granule;
> - u64 size = npages * PAGE_SIZE;
> + __u8 map_mode = map->bparam.map_mode;
> int ret = 0;
>
> - buf = alloc_pages_exact(size, GFP_KERNEL);
> - if (!buf)
> + struct map_benchmark_ops *mb_ops = dma_map_benchmark_ops[map_mode];
> + void *mparam = mb_ops->prepare(map);
> +
> + if (!mparam)
> return -ENOMEM;
>
> while (!kthread_should_stop()) {
> @@ -49,23 +132,10 @@ static int map_benchmark_thread(void *data)
> ktime_t map_stime, map_etime, unmap_stime, unmap_etime;
> ktime_t map_delta, unmap_delta;
>
> - /*
> - * 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.
> - */
> - if (map->dir != DMA_FROM_DEVICE)
> - memset(buf, 0x66, size);
> -
> map_stime = ktime_get();
> - dma_addr = dma_map_single(map->dev, buf, size, map->dir);
> - if (unlikely(dma_mapping_error(map->dev, dma_addr))) {
> - pr_err("dma_map_single failed on %s\n",
> - dev_name(map->dev));
> - ret = -ENOMEM;
> + ret = mb_ops->do_map(mparam);
> + if (ret)
> goto out;
> - }
> map_etime = ktime_get();
> map_delta = ktime_sub(map_etime, map_stime);
>
> @@ -73,7 +143,8 @@ static int map_benchmark_thread(void *data)
> ndelay(map->bparam.dma_trans_ns);
>
> unmap_stime = ktime_get();
> - dma_unmap_single(map->dev, dma_addr, size, map->dir);
> + mb_ops->do_unmap(mparam);
> +
> unmap_etime = ktime_get();
> unmap_delta = ktime_sub(unmap_etime, unmap_stime);
>
> @@ -108,7 +179,7 @@ static int map_benchmark_thread(void *data)
> }
>
> out:
> - free_pages_exact(buf, size);
> + mb_ops->unprepare(mparam);
> return ret;
> }
>
> @@ -209,6 +280,11 @@ static long map_benchmark_ioctl(struct file *file, unsigned int cmd,
>
> switch (cmd) {
> case DMA_MAP_BENCHMARK:
> + if (map->bparam.map_mode >= DMA_MAP_MODE_MAX) {
> + pr_err("invalid map mode\n");
> + return -EINVAL;
> + }
> +
> if (map->bparam.threads == 0 ||
> map->bparam.threads > DMA_MAP_MAX_THREADS) {
> pr_err("invalid thread number\n");
> --
> 2.33.0
>
Thanks
Barry
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