From: Alan Stern Date: Tue, 20 May 2008 20:59:33 +0000 (-0400) Subject: USB: EHCI: fix performance regression X-Git-Tag: v2.6.26-rc5~38^2~8 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa38dfcc56b5f6cce787f9aaa5d1830509213802;p=pandora-kernel.git USB: EHCI: fix performance regression This patch (as1099) fixes a performance regression in ehci-hcd. The fundamental problem is that queue headers get removed from the schedule too quickly, since the code checks for a counter advancing rather than making an actual time-based check. The latency involved in removing the queue header and then relinking it can severely degrade certain kinds of workloads. The patch replaces a simple counter with a timestamp derived from the controller's uframe value. In addition, the delay for unlinking an idle queue header is increased from 5 ms to 10 ms; since some controllers (nVidia) have a latency of up to 1 ms for unlinking, this reduces the relative impact from 20% to 10%. Finally, a logical error left over from the IAA watchdog-timer conversion is corrected. Now the driver will always either unlink an idle queue header or set up a timer to unlink it later. The old code would sometimes fail to do either. Signed-off-by: Alan Stern Cc: David Brownell Cc: Leonid Signed-off-by: Greg Kroah-Hartman --- Reading git-diff-tree failed