From: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
To: james.harper@bendigoit.com.au, xen-devel@lists.xensource.com
Subject: Re: pvusb performance
Date: Mon, 14 Sep 2009 14:45:11 +0900 [thread overview]
Message-ID: <4AADD867.1090809@jp.fujitsu.com> (raw)
In-Reply-To: <AEC6C66638C05B468B556EA548C1A77D0177D283@trantor>
James,
> Okay maybe I'm a bit confused then.
>
> When Windows gave me a URB with 65536 bytes of data, I set buffer_length
> to 65536 and filled up the SG registers accordingly, but usbback gave me
> an error. When I break it into 512 byte (packet size) chunks it works
> okay. I just assumed that you have to give usbback requests with less
> that 'max packet size' of data.
>
> Maybe the cause of my error was somewhere else? I'll try it again.
If you transfer 65536 bytes of data, you should change the
USBIF_MAX_SEGMENTS_PER_REQUESTS value to 16 or more.
It is defined in include/xen/interface/io/usbif.h
You need to recompile the drivers.
Request size and MAX_RING_SIZE are trade-off.
I defined this value empirically.
If the value is about up to 20, it doesn't affect the performance
of memory stick.
Regards,
Noboru
next prev parent reply other threads:[~2009-09-14 5:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-12 3:57 pvusb performance James Harper
2009-09-14 0:55 ` Noboru Iwamatsu
2009-09-14 1:19 ` James Harper
2009-09-14 2:36 ` Noboru Iwamatsu
2009-09-14 5:19 ` James Harper
2009-09-14 5:45 ` Noboru Iwamatsu [this message]
2009-09-14 5:49 ` James Harper
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