From patchwork Mon Oct 8 07:51:36 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [12/12] ehci: Speed up the timer of raising int from the async schedule Date: Sun, 07 Oct 2012 21:51:36 -0000 From: Hans de Goede X-Patchwork-Id: 189924 Message-Id: <1349682696-3046-13-git-send-email-hdegoede@redhat.com> To: Gerd Hoffmann Cc: Hans de Goede , qemu-devel@nongnu.org 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 --- 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 fb3547d..5056618 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) \ @@ -1546,6 +1547,9 @@ 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; + } } } @@ -2528,8 +2532,15 @@ 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); } }