diff options
| author | David Brownell <dbrownell@users.sourceforge.net> | 2008-06-03 22:21:55 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2008-07-21 15:16:27 -0700 |
| commit | b963801164618e25fbdc0cd452ce49c3628b46c8 (patch) | |
| tree | 149c888f19921f356607c8d7a1c1001e148450ba /drivers/usb/host/ehci-hcd.c | |
| parent | 38f3ad5e7463d4dd490a8081a5f3f9f2dec7ecd6 (diff) | |
USB: ehci-hcd unlink speedups
This patch fixes some performance bugs observed with some workloads
when unlinking EHCI queue header (QH) descriptors from the async ring
(control/bulk schedule).
The mechanism intended to defer unlinking an empty QH (so there is no
penalty in common cases where it's quickly reused) was not working as
intended. Sometimes the unlink was scheduled:
- too quickly ... which can be a *strong* negative effect, since
that QH becomes unavailable for immediate re-use;
- too slowly ... wasting DMA cycles, usually a minor issue except
for increased bus contention and power usage;
Plus there was an extreme case of "too slowly": a logical error in the
IAA watchdog-timer conversion meant that sometimes the unlink never
got scheduled.
The fix replaces a simple counter with a timestamp derived from the
controller's 8 KHz microframe counter, and adjusts the timer usage
for some issues associated with HZ being less than 8K.
(Based on a patch originally by Alan Stern, and good troubleshooting
from Leonid.)
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Leonid <leonidv11@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/host/ehci-hcd.c')
| -rw-r--r-- | drivers/usb/host/ehci-hcd.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 369a8a5ea7b..d9d53f289ca 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -84,7 +84,7 @@ static const char hcd_name [] = "ehci_hcd"; #define EHCI_IAA_MSECS 10 /* arbitrary */ #define EHCI_IO_JIFFIES (HZ/10) /* io watchdog > irq_thresh */ #define EHCI_ASYNC_JIFFIES (HZ/20) /* async idle timeout */ -#define EHCI_SHRINK_JIFFIES (HZ/200) /* async qh unlink delay */ +#define EHCI_SHRINK_FRAMES 5 /* async qh unlink delay */ /* Initial IRQ latency: faster than hw default */ static int log2_irq_thresh = 0; // 0 to 6 |