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Message-ID: <CAGsJ_4x7u00HVsa11cw_r6Mb3x0Ls-9tCg2HcUs=KvoVX=Vhvg@mail.gmail.com>
Date: Mon, 7 Apr 2025 17:50:42 +1200
From: Barry Song <21cnbao@...il.com>
To: Qinxin Xia <xiaqinxin@...wei.com>
Cc: chenxiang66@...ilicon.com, 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
Subject: Re: [PATCH 2/3] dma-mapping: benchmark: add support for dma_map_sg
On Wed, Feb 12, 2025 at 3:27 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 | 1 +
> kernel/dma/map_benchmark.c | 102 ++++++++++++++++++++++++++++++++++
> 2 files changed, 103 insertions(+)
>
> diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
> index 054db02a03a7..a9c1a104ba4f 100644
> --- a/include/linux/map_benchmark.h
> +++ b/include/linux/map_benchmark.h
> @@ -17,6 +17,7 @@
>
> enum {
> DMA_MAP_SINGLE_MODE,
> + DMA_MAP_SG_MODE,
> DMA_MAP_MODE_MAX
> };
>
> diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
> index d8ec0ce058d8..b5828eeb3db7 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>
>
> @@ -111,8 +112,109 @@ 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;
> +
> + struct dma_sg_map_param *mparam __free(kfree) = kzalloc(sizeof(*mparam), GFP_KERNEL);
> + if (!mparam)
> + return NULL;
> +
> + mparam->npages = map->bparam.granule;
Please add comments explaining that "granule" serves as nents in SG
mode, and that each SG entry corresponds to a single page.
Otherwise, in single mode, the granule represents what we map and
unmap as a whole in a single operation.
I mean, make the code below clearly express what you are doing:
__u32 granule; /* how many PAGE_SIZE will do map/unmap once a time */
> + 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 err1;
> +
> + if (sg_alloc_table(&mparam->sgt, mparam->npages, GFP_KERNEL))
> + goto err2;
> +
> + for_each_sgtable_sg(&mparam->sgt, sg, i) {
> + mparam->buf[i] = (void *)__get_free_page(GFP_KERNEL);
> + if (!mparam->buf[i])
> + goto err3;
> +
> + 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);
> +
> +err3:
> + while (i-- > 0)
> + free_page((unsigned long)mparam->buf[i]);
> +
> + pr_err("dma_map_sg failed get free page on %s\n", dev_name(mparam->dev));
> + sg_free_table(&mparam->sgt);
> +err2:
> + pr_err("dma_map_sg failed alloc sg table on %s\n", dev_name(mparam->dev));
> + kfree(mparam->buf);
> +err1:
> + pr_err("dma_map_sg failed alloc mparam buf on %s\n", dev_name(mparam->dev));
> + return NULL;
I assume allocation failures will already trigger their own warnings, so your
pr_err isn't necessary. BTW, please replace err1, err2, err3 with something
meaningful.
> +}
> +
> +static void dma_sg_map_benchmark_unprepare(void *arg)
> +{
> + 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);
> + if (!sg_mapped) {
> + pr_err("dma_map_sg failed on %s\n", dev_name(mparam->dev));
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +static int dma_sg_map_benchmark_do_unmap(void *arg)
void
> +{
> + struct dma_sg_map_param *mparam = arg;
> +
> + dma_unmap_sg(mparam->dev, mparam->sgt.sgl, mparam->npages,
> + mparam->dma_dir);
> +
> + return 0;
drop it.
> +}
> +
> +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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