Hi Wolfgang,
I'm not so sure about that. Once the interrupt is finished being serviced, the scheduler should immediately wake up and service any blocked processes rather than sitting idle for one CONFIG_HZ period (4 ms when CONFIG_HZ=250). At least that's my intuition. As I mentioned in my previous email, I will try strace and see what it shows. The problem may not be in USB but something is weird somewhere. Thanks again for your comments. It's useful to have a few people thinking about this. Regards. ----- Original Message ---- From: WolfgangMües <[EMAIL PROTECTED]> To: linux-usb-devel@lists.sourceforge.net Sent: Friday, October 13, 2006 11:53:35 PM Subject: Re: [linux-usb-devel] USB performance bug since kernel 2.6.13 (CRITICAL???) On Saturday 14 October 2006 01:02, Open Source wrote: > Either the problem is in the ehci code or in devio.c. In > devio.c the user space process calls an ioctl to reap the > urb (blocking until it is complete). The asynchronous > callback for the urb is called when the urb is unlinked > and that callback (async_completed in devio.c) signals > the wait object that the ioctl has added to the wait queue. The wakeup adds the waiting user process to the list of running processes, and the next timer tick will schedule this user process. And this is the delay you get: from the time of the wakeup call to the time the schedule is done. And if the schedule is done with 100 Hz, you will get a mean value of 5ms delay. regards Wolfgang -- Das Leben kann nur rückwärts verstanden, muß aber vorwärts gelebt werden. ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
