On Thu, 10 Aug 2006, Thorsten Wiedemer wrote: > Hi list ! > > We use a fairly large usb tree with about 12 hubs and 18 high speed devices > to build a control surface. > With kernel 2.6.8.1 it took about 8 seconds from plugin of the first hub > (where all other hubs/devices are connected) to the root hub until all > hubs/devices where "found" and announced in "/var/log/messages". > With kernel 2.6.15 this time increased to about 17seconds. That doubles the > time we need to get our surface working. > The distribution we use is a "self made" one, so in this test we only > changed the kernel and the appropriate drivers. udev and the hotplug > environment were the same in both cases. > > This is perhaps a stupid question, but is there a possibility to speed up > the connect handling (without rewriting the whole usb drivers ...) in the > newer kernel ? > > Any hints are welcome.
You shouldn't make timing measurements based on when things show up in /var/log/messages. That file is maintained by the syslog daemon, which does not necessarily add entries as soon as they are available. Instead you should use dmesg (there is a CONFIG option to add high-resolution timestamps to the log entries in later kernels), or monitor the contents of /proc/bus/usb/devices. It would help to have more detailed timing comparisons, to see where the extra time is being spent. I'm not aware of any great amount of slack in the USB drivers, although usb-storage does include a configurable delay. Changes in udev and hotplug are of course completely separate from the kernel's drivers. Alan Stern ------------------------------------------------------------------------- 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
