From 44272b0f88247e2d2960c0ef19b546c206a10080 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Wed, 24 Oct 2012 18:14:02 +0200 Subject: ehci: Speed up the timer of raising int from the async schedule 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 Signed-off-by: Gerd Hoffmann --- hw/usb/hcd-ehci.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c index f9ae05e71d..d600f08f6b 100644 --- a/hw/usb/hcd-ehci.c +++ b/hw/usb/hcd-ehci.c @@ -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; + } } } @@ -2504,8 +2508,15 @@ 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); } } -- cgit v1.2.1