Hi, On Friday 13 October 2006 21:31, Open Source wrote: > Thanks for the input. However, I am not understanding > exactly why kernel mode is treated any differently than > user mode for this sort of thing. I am looking at the code > in ehci-q.c and ehci-hcd.c. > > It seems like the unlinking of completed URBs > happens asynchronously on a timer. This is a > surprise to me since I thought this was happening > on an IRQ from the host controller.
You are not the only one - I am surprised too. I am sure the EHCI maintainer can explain this. Maybe the heavy interrupt load for EHCI is too much for some machines.... > But if what I'm > surmising is correct it would explain everything > I am seeing. I'm not able to ascertain how > user mode drivers are treated differently than > kernel mode drivers in this regard. User mode drivers suffer from the latency of the sheduler, so they can't be better than kernel drivers. > Besides, we count on sub-10 ms response times all the > time in user mode. Take for example, the access of a file. > If opening a file had a fixed latency of 4 ms, people > would be up in arms. But the latency is not fix in user mode ... it may be even 100ms because 10 other processes are running on the machine. 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
