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Message-ID: <CAGsJ_4zBHVwc3A67Wff3u0aypuPv6h25B_YdDqG5j9FmBOXn8g@mail.gmail.com>
Date: Wed, 7 May 2025 14:39:10 +1200
From: Barry Song <21cnbao@...il.com>
To: Qinxin Xia <xiaqinxin@...wei.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 v2 3/4] dma-mapping: benchmark: add support for dma_map_sg
On Tue, May 6, 2025 at 3:01 PM Qinxin Xia <xiaqinxin@...wei.com> wrote:
>
> Support for dma scatter-gather mapping and is intended for testing
> mapping performance. It achieves by introducing the dma_sg_map_param
> structure and related functions, which enable the implementation of
> scatter-gather mapping preparation, mapping, and unmapping operations.
> Additionally, the dma_map_benchmark_ops array is updated to include
> operations for scatter-gather mapping. This commit aims to provide
> a wider range of mapping performance test to cater to different scenarios.
>
> Signed-off-by: Qinxin Xia <xiaqinxin@...wei.com>
> ---
> include/linux/map_benchmark.h | 43 ++++++++++----
> kernel/dma/map_benchmark.c | 102 ++++++++++++++++++++++++++++++++++
> 2 files changed, 133 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
> index 5294dfd1870f..bf8c9ade43fd 100644
> --- a/include/linux/map_benchmark.h
> +++ b/include/linux/map_benchmark.h
> @@ -17,22 +17,41 @@
>
> enum {
> DMA_MAP_SINGLE_MODE,
> + DMA_MAP_SG_MODE,
> DMA_MAP_MODE_MAX
> };
>
> +/**
> + * struct map_benchmark - Benchmarking data for DMA mapping operations.
> + * @avg_map_100ns: Average map latency in 100ns.
> + * @map_stddev: Standard deviation of map latency.
> + * @avg_unmap_100ns: Average unmap latency in 100ns.
> + * @unmap_stddev: Standard deviation of unmap latency.
> + * @threads: Number of threads performing map/unmap operations in parallel.
> + * @seconds: Duration of the test in seconds.
> + * @node: NUMA node on which this benchmark will run.
> + * @dma_bits: DMA addressing capability.
> + * @dma_dir: DMA data direction.
> + * @dma_trans_ns: Time for DMA transmission in ns.
> + * @granule: Number of PAGE_SIZE units to map/unmap at once.
> + In SG mode, this represents the number of scatterlist entries.
> + In single mode, this represents the total size of the mapping.
> + * @map_mode: Mode of DMA mapping.
> + * @expansion: Reserved for future use.
> + */
> 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 avg_map_100ns;
> + __u64 map_stddev;
> + __u64 avg_unmap_100ns;
> __u64 unmap_stddev;
> - __u32 threads; /* how many threads will do map/unmap in parallel */
> - __u32 seconds; /* how long the test will last */
> - __s32 node; /* which numa node this benchmark will run on */
> - __u32 dma_bits; /* DMA addressing capability */
> - __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 map_mode; /* the mode of dma map */
> - __u8 expansion[75]; /* For future use */
> + __u32 threads;
> + __u32 seconds;
> + __s32 node;
> + __u32 dma_bits;
> + __u32 dma_dir;
> + __u32 dma_trans_ns;
> + __u32 granule;
> + __u8 map_mode;
> + __u8 expansion[75];
> };
> #endif /* _KERNEL_DMA_BENCHMARK_H */
> diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
> index f04973eba1d8..72cd2c5f839e 100644
> --- a/kernel/dma/map_benchmark.c
> +++ b/kernel/dma/map_benchmark.c
> @@ -17,6 +17,7 @@
> #include <linux/module.h>
> #include <linux/pci.h>
> #include <linux/platform_device.h>
> +#include <linux/scatterlist.h>
> #include <linux/slab.h>
> #include <linux/timekeeping.h>
>
> @@ -110,8 +111,109 @@ static struct map_benchmark_ops dma_single_map_benchmark_ops = {
> .do_unmap = dma_single_map_benchmark_do_unmap,
> };
>
> +struct dma_sg_map_param {
> + struct sg_table sgt;
> + struct device *dev;
> + void **buf;
> + u32 npages;
> + u32 dma_dir;
> +};
> +
> +static void *dma_sg_map_benchmark_prepare(struct map_benchmark_data *map)
> +{
> + struct scatterlist *sg;
> + int i = 0;
I'm not sure we need `i = 0`; perhaps just `int i` would be sufficient.
> +
> + struct dma_sg_map_param *mparam __free(kfree) = kzalloc(sizeof(*mparam), GFP_KERNEL);
> + if (!mparam)
> + return NULL;
> +
> + /*
> + * Set the number of scatterlist entries based on the granule.
> + * In SG mode, 'granule' represents the number of scatterlist entries.
> + * Each scatterlist entry corresponds to a single page.
> + */
> + mparam->npages = map->bparam.granule;
> + mparam->dma_dir = map->bparam.dma_dir;
> + mparam->dev = map->dev;
> + mparam->buf = kmalloc_array(mparam->npages, sizeof(*mparam->buf),
> + GFP_KERNEL);
> + if (!mparam->buf)
> + goto out;
> +
> + if (sg_alloc_table(&mparam->sgt, mparam->npages, GFP_KERNEL))
> + goto free_buf;
> +
> + for_each_sgtable_sg(&mparam->sgt, sg, i) {
> + mparam->buf[i] = (void *)__get_free_page(GFP_KERNEL);
> + if (!mparam->buf[i])
> + goto free_page;
> +
> + if (mparam->dma_dir != DMA_FROM_DEVICE)
> + memset(mparam->buf[i], 0x66, PAGE_SIZE);
> +
> + sg_set_buf(sg, mparam->buf[i], PAGE_SIZE);
> + }
> +
> + return_ptr(mparam);
> +
> +free_page:
> + while (i-- > 0)
> + free_page((unsigned long)mparam->buf[i]);
> +
> + sg_free_table(&mparam->sgt);
> +free_buf:
> + kfree(mparam->buf);
> +out:
> + return NULL;
> +}
> +
> +static void dma_sg_map_benchmark_unprepare(void *arg)
The term "arg" is meaningless for a function argument, as it's already implied
that it is an argument.
> +{
> + struct dma_sg_map_param *mparam = arg;
> + int i;
> +
> + for (i = 0; i < mparam->npages; i++)
> + free_page((unsigned long)mparam->buf[i]);
> +
> + sg_free_table(&mparam->sgt);
> +
> + kfree(mparam->buf);
> + kfree(mparam);
> +}
> +
> +static int dma_sg_map_benchmark_do_map(void *arg)
> +{
> + struct dma_sg_map_param *mparam = arg;
> +
> + int sg_mapped = dma_map_sg(mparam->dev, mparam->sgt.sgl,
> + mparam->npages, mparam->dma_dir);
int ret.
> + if (!sg_mapped) {
> + pr_err("dma_map_sg failed on %s\n", dev_name(mparam->dev));
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +static void dma_sg_map_benchmark_do_unmap(void *arg)
> +{
> + struct dma_sg_map_param *mparam = arg;
> +
> + dma_unmap_sg(mparam->dev, mparam->sgt.sgl, mparam->npages,
> + mparam->dma_dir);
> +}
> +
> +static struct map_benchmark_ops dma_sg_map_benchmark_ops = {
> + .prepare = dma_sg_map_benchmark_prepare,
> + .unprepare = dma_sg_map_benchmark_unprepare,
> + .do_map = dma_sg_map_benchmark_do_map,
> + .do_unmap = dma_sg_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,
> + [DMA_MAP_SG_MODE] = &dma_sg_map_benchmark_ops,
> };
>
> static int map_benchmark_thread(void *data)
> --
> 2.33.0
>
Thanks
barry
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