Hello Group, Kindly provide any little input. On Sat, Feb 20, 2010 at 11:58 AM, Pratik Prajapati <pratik.prajapati@xxxxxxxxx> wrote: > Hello Swami, > > Thank you for your reply. > > My issue is, > > I want to make best use of DMA to get better performance. (better > performance means less CPU usage and less interrupts.) My clients > wants better performance, as he is going to run CPU hungry application > which will do USB BULK+ISO xfer. > > With DMA, my BULK xfer takes same CPU capared to 'without DMA', but I > get lesser intereputs 'WITH DMA'. > With DMA, my ISO xfer takes more CPU capared to 'without DMA', and I > see same no. of interrupts 'WITH DMA'. > > So I'm getting advantage of using DMA in BULK xfer, but ISO xfer gets > worst( as CPU usage goes very high in ISO xfer because of ksoftirqd). > > For ISO xfer,Without DMA my CPU usage is total 1% to 6% (i.e. 1% to 5% > audio player app takes + 0% to 1% ksoftirqd takes). > For ISO xfer, With DMA my CPU usage is total 20% to 32% (i.e. 0% to 2% > audio player app takes + 20% to 30% ksoftirqd takes). > > With DMA, I see overall CPU usage go very high compared to 'without > DMA' i.e. for ISO xfer. because of ksoftirqd. > I think musb schdules tasklets in davinci_interrupt isr for DMA. Which > inturn makes a lot of sort irqs and so ksoftirqd eats of a lot of > CPU(around 20% to 30%). > > with DMA, ISO xfer gets worst as ksoftirqd eats up a lot of CPU > campared to "WITHOUT DMA" > > Kindly suggest me how can I get best performace with DMA for both ISO and BULK? > > Thank you in advance. > > On Sat, Feb 20, 2010 at 12:57 AM, Subbrathnam, Swaminathan > <swami.iyer@xxxxxx> wrote: >> Pratik, >> The increased interrupt activity during ISO transactions is expected. >> >> Can you provide information on the actual issue you are facing. Are you not able to stream/run application etc. due to the increased interrupts? >> >> Regards >> Swami >> >>> -----Original Message----- >>> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb- >>> owner@xxxxxxxxxxxxxxx] On Behalf Of Pratik Prajapati >>> Sent: Friday, February 19, 2010 3:06 PM >>> To: linux-usb@xxxxxxxxxxxxxxx >>> Subject: need to know about usbaudio. >>> >>> Hello, >>> >>> I'm doing playback/record with usbaudio on TI musb with ALSA. >>> >>> My concern is, in isochronus mode (with CPPI DMA) I see a lot of >>> interrupts and so ksoftirqd takes up to 30% CPU in addition to Audio >>> application. And in bulk mode(with CPPI DMA) I see less interrupts and >>> also ksoftirqd is taking around 15% CPU in addition to the >>> application. Is there any way by which I can get lesser interrupts in >>> sochronus mode (with CPPI DMA)? >>> >>> my linux is: 2.6.10_mvl401, with >>> musb_hdrc: version 2.2a/db-0.4.8 [cppi-dma] [host] [debug=1] >>> musb_hdrc: ConfigData=0x06 (UTMI-8, dyn FIFOs, SoftConn) >>> musb_hdrc: MHDRC RTL version 1.300 >>> musb_hdrc: USB Host mode controller at c8002000 using DMA, IRQ 12 >>> musb_hdrc musb_hdrc: new USB bus registered, assigned bus number 1 >>> >>> I have observed that whether I play 8KHZ audio or 44KHZ audio, I see >>> iso_frame_desc (packed in urb) ramains of same length, i.e. 176 bytes. >>> e.g. >>> I played 8KHZ audio and found that, musb is gets total 4 >>> iso_frame_desc in each URB. size of each iso_frame_desc is 176 bytes. >>> I played 44KHZ audio and found that, musb is gets total 4 >>> iso_frame_desc in each URB. size of each iso_frame_desc is 176 bytes. >>> In each URB musb gets 4 iso_frame_desc, which is fixed by variable >>> 'static int nrpacks' in usbaudio.c. >>> >>> CPPI DMA makes buffer discriptors of each iso_frame_desc, which is >>> very small chunk. >>> >>> Does it make sense that usbaudio passes larger iso_frame_desc to musb >>> ( right now I'm getting 176 bytes iso_frame_desc each time)? so that >>> CPPI DMA will send lesser interrupts to CPU. >>> >>> Please let me know if more information is required from my side. >>> >>> -- >>> Regards, >>> Pratik PRAJAPATI >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-usb" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > > > > -- > Regards, > Pratik PRAJAPATI > -- Regards, Pratik PRAJAPATI -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
