> -----Original Message----- > From: John Garry > Sent: Monday, November 2, 2020 10:19 PM > To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>; > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; hch@xxxxxx; robin.murphy@xxxxxxx; > m.szyprowski@xxxxxxxxxxx > Cc: linux-kselftest@xxxxxxxxxxxxxxx; Shuah Khan <shuah@xxxxxxxxxx>; Joerg > Roedel <joro@xxxxxxxxxx>; Linuxarm <linuxarm@xxxxxxxxxx>; xuwei (O) > <xuwei5@xxxxxxxxxx>; Will Deacon <will@xxxxxxxxxx> > Subject: Re: [PATCH v3 1/2] dma-mapping: add benchmark support for > streaming DMA APIs > > On 02/11/2020 08:06, Barry Song wrote: > > Nowadays, there are increasing requirements to benchmark the performance > > of dma_map and dma_unmap particually while the device is attached to an > > IOMMU. > > > > This patch enables the support. Users can run specified number of threads > > to do dma_map_page and dma_unmap_page on a specific NUMA node with > the > > specified duration. Then dma_map_benchmark will calculate the average > > latency for map and unmap. > > > > A difficulity for this benchmark is that dma_map/unmap APIs must run on > > a particular device. Each device might have different backend of IOMMU or > > non-IOMMU. > > > > So we use the driver_override to bind dma_map_benchmark to a particual > > device by: > > For platform devices: > > echo dma_map_benchmark > /sys/bus/platform/devices/xxx/driver_override > > echo xxx > /sys/bus/platform/drivers/xxx/unbind > > echo xxx > /sys/bus/platform/drivers/dma_map_benchmark/bind > > > > For PCI devices: > > echo dma_map_benchmark > > /sys/bus/pci/devices/0000:00:01.0/driver_override > > echo 0000:00:01.0 > /sys/bus/pci/drivers/xxx/unbind > > echo 0000:00:01.0 > /sys/bus/pci/drivers/dma_map_benchmark/bind > > > > Cc: Joerg Roedel <joro@xxxxxxxxxx> > > Cc: Will Deacon <will@xxxxxxxxxx> > > Cc: Shuah Khan <shuah@xxxxxxxxxx> > > Cc: Christoph Hellwig <hch@xxxxxx> > > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > > Cc: Robin Murphy <robin.murphy@xxxxxxx> > > Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx> > > --- > > -v3: > > * fix build issues reported by 0day kernel test robot > > -v2: > > * add PCI support; v1 supported platform devices only > > * replace ssleep by msleep_interruptible() to permit users to exit > > benchmark before it is completed > > * many changes according to Robin's suggestions, thanks! Robin > > - add standard deviation output to reflect the worst case > > - check users' parameters strictly like the number of threads > > - make cache dirty before dma_map > > - fix unpaired dma_map_page and dma_unmap_single; > > - remove redundant "long long" before ktime_to_ns(); > > - use devm_add_action() > > > > kernel/dma/Kconfig | 8 + > > kernel/dma/Makefile | 1 + > > kernel/dma/map_benchmark.c | 296 > +++++++++++++++++++++++++++++++++++++ > > 3 files changed, 305 insertions(+) > > create mode 100644 kernel/dma/map_benchmark.c > > > > diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig > > index c99de4a21458..949c53da5991 100644 > > --- a/kernel/dma/Kconfig > > +++ b/kernel/dma/Kconfig > > @@ -225,3 +225,11 @@ config DMA_API_DEBUG_SG > > is technically out-of-spec. > > > > If unsure, say N. > > + > > +config DMA_MAP_BENCHMARK > > + bool "Enable benchmarking of streaming DMA mapping" > > + help > > + Provides /sys/kernel/debug/dma_map_benchmark that helps with > testing > > + performance of dma_(un)map_page. > > Since this is a driver, any reason for which it cannot be loadable? If > so, it seems any functionality would depend on DEBUG FS, I figure that's > just how we work for debugfs. We depend on kthread_bind_mask which isn't an export_symbol. Maybe worth to send a patch to export it? > > Thanks, > John > > > + > > + See tools/testing/selftests/dma/dma_map_benchmark.c > > diff --git a/kernel/dma/Makefile b/kernel/dma/Makefile > > index dc755ab68aab..7aa6b26b1348 100644 > > --- a/kernel/dma/Makefile > > +++ b/kernel/dma/Makefile Thanks Barry
