|
From: | Hans de Goede |
Subject: | Re: [Qemu-devel] [PATCH 06/22] ehci: Speed up the timer of raising int from the async schedule |
Date: | Mon, 15 Oct 2012 15:00:01 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121009 Thunderbird/16.0 |
Hi, On 10/15/2012 01:17 PM, Gerd Hoffmann wrote:
On 10/15/12 12:38, Hans de Goede wrote: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.Why not just set async_stepdown to 0?
We already do that whenever we run a package completion (it get sets when we move to the executing stage). What this patch does is request the frame timer to run again in 500 usecs instead of after 1 ms, thus making us see and process async transfers faster when they are queued up in response to just completed packages (which we've told the guest about with the int interrupt). This makes the USB-bus / device idle time between any 2 transfers of the 3 transfer involving USB storage BOT time shorter, thereby speeding things up. Regards, Hans
[Prev in Thread] | Current Thread | [Next in Thread] |