From: Richard Miller <9fans@hamnavoe.com>
To: 9fans@9fans.net
Subject: Re: [9fans] usbether
Date: Sat, 29 Sep 2012 19:01:42 +0100 [thread overview]
Message-ID: <896eab203042b2e267eb2b12d585a553@hamnavoe.com> (raw)
In-Reply-To: <d07dd7e7d5190bfda4e065a12d8b724c@kw.quanstro.net>
> why doesn't the device do the buffering?
By "device" do you mean the hardware usb/ether adapter? It does some
buffering - you can configure it to "burst" as many ether input packets
as will fit in N 512-byte usb packets, in each usb input operation.
I've got N=37 because that's what the linux driver does; of course
there's no documentation to explain what the allowed range is or
what the consequences of varying it would be. As far as I can see
there's no "overrun" flag for the device to tell me I've missed
reading some packets.
> or is the problem
> that usb/ether essentially an event loop of <read packet> <write packet>
> and any delays in that pipeline accumulate?
Almost: it's a pipeline of one thread reading a buffer full of packets,
splitting it up, and sending a packet at a time to a second thread, which
writes them to the kernel packet ethernet interface, which stores them
in a Buf queue.
next prev parent reply other threads:[~2012-09-29 18:01 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-29 16:16 Richard Miller
2012-09-29 16:39 ` Gorka Guardiola
2012-09-29 17:03 ` erik quanstrom
2012-09-29 18:01 ` Richard Miller [this message]
2012-09-29 18:19 ` Gorka Guardiola
2012-09-29 18:24 ` Richard Miller
2012-09-29 21:38 ` Gorka Guardiola
2012-09-29 21:46 ` Richard Miller
2012-09-29 21:48 ` erik quanstrom
2012-10-01 19:20 ` Richard Miller
2012-09-30 9:20 ` Charles Forsyth
2012-09-30 10:24 ` Richard Miller
2012-09-30 13:54 ` Charles Forsyth
2012-09-29 18:41 ` erik quanstrom
2012-09-29 19:49 ` Charles Forsyth
2012-09-30 23:29 ` Tristan
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