Hi Russell, > On Tue, Aug 14, 2012 at 12:54:00PM +0200, Jiri Kosina wrote: > > Actually, Henrik (added to CC) has been doing some latency improvements > > both for input core in general, and for HID devices as well lately. I > > still have his patchset in my to-review queue, as I have just came back > > from offline vacation, but the patch below definitely can't hurt and > > should significantly lower the time spent in handling the irq for hid > > device in common situation (i.e. noone listening for debugfs events). > > > > Could you please measure how much it helps on your system? > > Ok, it looks like it's changed the maximum USB interrupt execution > time from around 364us to 255us. With the on-review input patches on top of that, the latency should drop further. I have measured a total of 2.5 times lower latency in other areas, so I would expect something like 150 us in 3.7 for your case. > If I also do a similar trick with the debug code in hid_input_report() > then I get down to 212us - iow, something like the patch below. Linus' master already has a patch for that code path, actually. > Given that debugfs is fairly ubiquitous in the kernel, and that this is > fairly invasive in terms of interrupt execution impact, wouldn't having > this debug code enabled by a separate Kconfig symbol be reasonable too? I would like that, too. Thanks, Henrik -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
