On Sun, 18 Apr 2004, Duncan Sands wrote: > > > gives correctness, but at the cost of a probable performance hit. In > > > later steps we can (1) turn dev->serialize into a rwsem > > > > Rwsems are _slower_ in the normal case of no contention. > > Right, but remember that dev->serialize is per device, not per interface. So if two > programs grab different interfaces of the same device using usbfs, or if multiple > threads in the same program beat on the same interface, then they could lose time > fighting for dev->serialize when in fact they could run in parallel. Personally I > doubt > it matters much, but since most of usbfs only requires read access to the data > structures > protected by dev->serialize, it seems logical to use a rwsem.
There was a lengthy discussion about this a few months ago. On the whole, people felt that using an rwsem wasn't a good idea. Personally, I think that contention for a single device will be very rare, so we don't need to consider it and can leave things as they are. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
