@@ -443,6 +443,7 @@ struct EHCIState {
uint64_t last_run_ns;
uint32_t async_stepdown;
+ bool int_req_by_async;
};
#define SET_LAST_RUN_CLOCK(s) \
@@ -1529,6 +1530,9 @@ static void ehci_execute_complete(EHCIQueue *q)
if (q->qh.token & QTD_TOKEN_IOC) {
ehci_raise_irq(q->ehci, USBSTS_INT);
+ if (q->async) {
+ q->ehci->int_req_by_async = true;
+ }
}
}
@@ -2503,8 +2507,15 @@ static void ehci_frame_timer(void *opaque)
}
if (need_timer) {
- expire_time = t_now + (get_ticks_per_sec()
+ /* If we've raised int, we speed up the timer, so that we quickly
+ * notice any new packets queued up in response */
+ if (ehci->int_req_by_async && (ehci->usbsts & USBSTS_INT)) {
+ expire_time = t_now + get_ticks_per_sec() / (FRAME_TIMER_FREQ * 2);
+ ehci->int_req_by_async = false;
+ } else {
+ expire_time = t_now + (get_ticks_per_sec()
* (ehci->async_stepdown+1) / FRAME_TIMER_FREQ);
+ }
qemu_mod_timer(ehci->frame_timer, expire_time);
}
}
Often the guest will queue up new packets in response to a packet, in the async schedule with its IOC flag set, completing. By speeding up the frame-timer, we notice these new packets earlier. This increases the speed (MB/s) of a Linux guest reading from a USB mass storage device by a factor of 1.15 on top of the "Improve latency of interrupt delivery" speed-ups, both with and without input pipelining enabled. I've not tested the speed-up of this patch without the "Improve latency of interrupt delivery" patch. Signed-off-by: Hans de Goede <hdegoede@redhat.com> --- hw/usb/hcd-ehci.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)