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List:       linux-usb-users
Subject:    Re: [Linux-usb-users] Why would ehci-hcd slow down the network?
From:       David Brownell <david-b () pacbell ! net>
Date:       2007-06-21 15:27:02
Message-ID: 200706210827.03355.david-b () pacbell ! net
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On Thursday 21 June 2007, Dirk Försterling wrote:
> Hi,
> 
> I just tried another PCI card (unfortunately, it's a VIA 6212L, too)
> but the symptoms remain the same: Shortly after inserting ehci-hcd,
> the system slows down and I get at most 1.89MB/s with the attached
> WD disk.
> 
> Any news on the meaning of the Start/End ASS messages? What else can
> I do in order to find the cause of the problem?

ISTR that previous email flagged the misbehavior of the async
schedule enable/disable as completely explaining the "slowdown"
issue ... the controller wasn't getting off the PCI bus when it
was told (because it has no work) to do so.  So it's sitting in
a tight loop DMAing lots of nothing, keeping other devices from
accessing the bus.

There was a patch to increase one of the lowlevel timeouts, and
I don't recall ever seeing feedback about whether that made the
problem go away.  A quick look suggests that the qh_link_async()
handshake() call timeout might be increased -- try 500, that's
disgustingly long given that the spec guarantees 125.

- Dave



> 
>   -dirk
> 
> On 04.05.2007 08:56 Dirk Försterling  wrote:
> > Alan Stern wrote:
> >> The patch below should help verify some of the assumptions in the driver.
> >> If they turn out to be wrong then we'll know where to look.  If they turn
> >> out to be right... then we'll be no better off.
> > 
> > Here's the dmesg outpout where the new messages come up. From my
> > limited understanding, this seems to mean that the expected problem does
> > NOT show up here, does it?
> > 
> > [...]
> > hub 1-0:1.0: port 1, status 0501, change 0001, 480 Mb/s
> > hub 1-0:1.0: debounce: port 1: total 100ms stable 100ms status 0x501
> > ehci_hcd 0000:00:13.2: port 1 high speed
> > ehci_hcd 0000:00:13.2: GetStatus port 1 status 001005 POWER sig=se0 PE CONNECT
> > usb 1-1: new high speed USB device using ehci_hcd and address 3
> > Start ASS: 0
> > End ASS: 8000
> > ehci_hcd 0000:00:13.2: port 1 high speed
> > ehci_hcd 0000:00:13.2: GetStatus port 1 status 001005 POWER sig=se0 PE CONNECT
> > Start ASS: 8000
> > End ASS: 8000
> > Start ASS: 8000
> > usb 1-1: default language 0x0409
> > usb 1-1: new device strings: Mfr=1, Product=2, SerialNumber=3
> > usb 1-1: Product: External HDD
> > usb 1-1: Manufacturer: Western Digital
> > usb 1-1: SerialNumber: <the serial number>
> > usb 1-1: uevent
> > usb 1-1: usb_probe_device
> > usb 1-1: configuration #1 chosen from 1 choice
> > usb 1-1: adding 1-1:1.0 (config #1, interface 0)
> > usb 1-1:1.0: uevent
> > drivers/usb/core/inode.c: creating file '003'
> > End ASS: 8000
> > [that's it. System slow]
> > 
> > 
> 
> 
> 
> -- 
>                    D i r k   F "o r s t e r l i n g
>                    r@zorbla.de  http://r.zorbla.de/
>                             -------------
>                 Huch nobHa'bogh veranganpu''e' yIvoqQo'
> 



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