linux-kernel - Re: [PATCH v6 3/3] tools/dma: Add dma_map

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Message-ID: <CAGsJ_4zkLF8Si6A0tvFNPGq2VJ8Md-Be=25K65XxSn-JWtCxbA@mail.gmail.com>
Date: Mon, 26 Jan 2026 10:51:11 +0800
From: Barry Song <21cnbao@...il.com>
To: Qinxin Xia <xiaqinxin@...wei.com>
Cc: jonathan.cameron@...wei.com, wangzhou1@...ilicon.com, 
	iommu@...ts.linux.dev, prime.zeng@...wei.com, fanghao11@...wei.com, 
	linux-kernel@...r.kernel.org, linuxarm@...wei.com
Subject: Re: [PATCH v6 3/3] tools/dma: Add dma_map_sg support

On Mon, Jan 12, 2026 at 5:34 PM Qinxin Xia <xiaqinxin@...wei.com> wrote:
>
> Support for dma_map_sg, add option '-m' to distinguish mode.
>
> i) Users can set option '-m' to select mode:
>    DMA_MAP_BENCH_SINGLE_MODE=0, DMA_MAP_BENCH_SG_MODE:=1
>    (The mode is also show in the test result).
> ii) Users can set option '-g' to set sg_nents
>     (total count of entries in scatterlist)
>     the maximum number is 1024. Each of sg buf size is PAGE_SIZE.
>     e.g
>     [root@...alhost]# ./dma_map_benchmark -m 1 -g 8 -t 8 -s 30 -d 2
>     dma mapping mode: DMA_MAP_BENCH_SG_MODE
>     dma mapping benchmark: threads:8 seconds:30 node:-1
>     dir:FROM_DEVICE granule/sg_nents: 8
>     average map latency(us):1.4 standard deviation:0.3
>     average unmap latency(us):1.3 standard deviation:0.3
>     [root@...alhost]# ./dma_map_benchmark -m 0 -g 8 -t 8 -s 30 -d 2
>     dma mapping mode: DMA_MAP_BENCH_SINGLE_MODE
>     dma mapping benchmark: threads:8 seconds:30 node:-1
>     dir:FROM_DEVICE granule/sg_nents: 8
>     average map latency(us):1.0 standard deviation:0.3
>     average unmap latency(us):1.3 standard deviation:0.5
>

What happens if m is set to 0 while g is set to 8?

Thanks
Barry