On Thu, Mar 09, 2023 at 09:30:00AM +0200, Tony Lindgren wrote: > * Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx> [230307 09:53]: > > On Mon, Mar 6, 2023 at 8:42 AM Tony Lindgren <tony@xxxxxxxxxxx> wrote: > > > > > > * Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx> [230228 08:01]: > > > > Any idea why the performance drop is so big? > > > > > > Maybe lots of interrupts and dma not being used for musb in this case? > > > > Using "irqtop -d 1", I get the following results: > > > > 3.18.1 LATENCY_OFF (16 ports): ca. 1000 IRQs/s INTC 17 47400000.dma-controller > > 3.18.1 LATENCY_ON (16 ports): ca. 4000 IRQs/s INTC 17 47400000.dma-controller > > > > 6.2.1 LATENCY_OFF (16 ports): ca. 300 IRQs/s INTC 17 47400000.dma-controller > > 6.2.1 LATENCY_ON (16 ports): ca. 1000 IRQs/s INTC 17 47400000.dma-controller > > Hmm I wonder what's causing that. Earlier the Ethernet gadget had some > alignment define tweak that made transfers faster. What kind of data > transfer are you testing with? > > > #zcat /proc/config.gz | grep CPP > > CONFIG_USB_TI_CPPI41_DMA=y > > CONFIG_TI_CPPI41=y > > From what I recall musb still handles short transfers with PIO, I think > this is the case also for cppi41 dma. Sounds like that does not explain > the difference you're seeing between 3.18 and 6.2 kernels though. I quickly scanned the changes on musb_cppi41.c and dma/cppi41.c between v3.18 and v5.4, but nothing stands out. I am wondering if this is something caused by outside of usb subsystem... -Bin.
