Hi Wolfgang and all, I really don't want to belabor this point, and there are surely more qualified people to chime in than myself, but let's take this thought experiment:
1) User space wants to access some data on the disk. 2) System calls enters the kernel 3) A request is sent to the disk. 4) The process "sleeps" to wait for the disk. (No other processes are running so only the idle loop is running at this point.) 5) An interrupt triggers back from the disk. 6) The process wakes up. Now if #6 didn't happen immediately, such user operations would slow appreciably as CONFIG_HZ is reduced. Maybe I misspoke by saying the "scheduler" runs for #6 to wake up. I don't know the internals of the wait queue infrastructure. But whatever it is, it has to wake up immediately. That's really the essence of the discussion here anyway. Please let me know if I'm missing something here. I don't want to turn this email list into an education on OSes...so I apologize in advance to all. I'd just like to get some clarity though. Cheers. ----- Original Message ---- From: WolfgangMües <[EMAIL PROTECTED]> To: linux-usb-devel@lists.sourceforge.net Sent: Saturday, October 14, 2006 10:09:03 AM Subject: Re: [linux-usb-devel] USB performance bug since kernel 2.6.13 (CRITICAL???) On Saturday 14 October 2006 18:40, Open Source wrote: > 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. Think about it... If _each_ interrupt would trigger the scheduler, you can bring the whole system down with a single fast-period interrupt in the system. The scheduler is triggered by the timer interrupt or if a process waits. 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
