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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 <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Hans de Goede 2012-10-24 18:14:02 +02:00 committed by Gerd Hoffmann
parent 0262f65aaa
commit 44272b0f88
1 changed files with 12 additions and 1 deletions
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13
hw/usb/hcd-ehci.c
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@ -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);
}
}