[prev in list] [next in list] [prev in thread] [next in thread] 

List:       netbsd-port-arm
Subject:    Re: Excessive interrupt time on Raspberry Pi
From:       Jason Thorpe <thorpej () me ! com>
Date:       2018-05-26 15:09:46
Message-ID: 1C85F27C-66A3-4E04-A00F-4FD2B685BBF9 () me ! com
[Download RAW message or body]



> On May 26, 2018, at 7:24 AM, Jared McNeill <jmcneill@invisible.ca> wrote:
> 
> Nick tells me the microframe scheduler has to run on the host if at least one \
> device is connected and since you can't remove the built-in hub or ethernet from \
> rpi, you're screwed. Raspbian kernel uses FIQ to help here..

Ah, of course.  Yah, a FIQ would help, but geez I hate doing board-specific code for \
generic drivers like that (mostly because it's hard to get the software abstractions \
right).

> 
> 
> On Sat, 26 May 2018, Jason Thorpe wrote:
> 
> > So, my Raspberry Pi is sitting completely idle other than an ssh session (over \
> > USB-connected-WiFi) and an instance of top(1) running: 
> > load averages:  0.02,  0.02,  0.00;               up 0+08:19:41        06:10:44
> > 22 processes: 21 sleeping, 1 on CPU
> > CPU states:  0.0% user,  0.0% nice,  0.0% system,  4.8% interrupt, 95.2% idle
> > Memory: 191M Act, 584K Inact, 12M Wired, 13M Exec, 170M File, 175M Free
> > Swap: 128M Total, 128M Free
> > 
> > That interrupt time is **insane**.
> > 
> > Turns out it's the USB:
> > 
> > bcm2835 pic timer3       3115038   99
> > bcm2835 pic Mailbox         1039    0
> > bcm2835 pic uart            7797    0
> > bcm2835 pic emmc           70272    2
> > bcm2835 pic dma0           18396    0
> > bcm2835 pic usb        251638013 8075
> > bcm2835 pic Doorbell0          4    0
> > Total                  254850559 8178
> > 
> > If I unplug my urtwn WiFi and reboot, the situation isn't any better; with \
> > nothing plugged into the USB ports, I'm still getting ~8K interrupts per second \
> > from USB: 
> > interrupt               total rate
> > bcm2835 pic timer3       9795  104
> > bcm2835 pic Mailbox         4    0
> > bcm2835 pic uart         3430   36
> > bcm2835 pic emmc        38303  407
> > bcm2835 pic dma0        12589  133
> > bcm2835 pic usb        770580 8197
> > bcm2835 pic Doorbell0       4    0
> > Total                  834705 8879
> > 
> > Do other platforms have use the DesignWare USB controller have a similar problem?
> > 
> > -- thorpej
> > 
> > 

-- thorpej


[prev in list] [next in list] [prev in thread] [next in thread]