Re: [PATCH v3 2/4] dma-mapping: benchmark: modify the framework to adapt to more map modes

[Qinxin Xia <xiaqinxin@huawei.com>]

On 2025/5/9 11:41:31, Barry Song <21cnbao@gmail.com> wrote:
> On Fri, May 9, 2025 at 2:02 PM Qinxin Xia <xiaqinxin@huawei.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@huawei.com>
> - stable@vger.kernel.org
> + Marek
> + Robin,
>
> Once the minor issues below are addressed, feel free to add:
>
> Reviewed-by: Barry Song <baohua@kernel.org>
OK
>> ---
>>   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

Thanks

Qinxin