linux-kernel - Re: [PATCH 5/5] usb_debug: EXPERIMENTAL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.44L0.0905071029200.3087-100000@iolanthe.rowland.org>
Date:	Thu, 7 May 2009 10:35:57 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jason Wessel <jason.wessel@...driver.com>, <greg@...ah.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] usb_debug: EXPERIMENTAL - poll hcd device to force
 writes

On Thu, 7 May 2009, Oliver Neukum wrote:

> On a fundamental note, thinking about this in terms of numbers of URBs
> is strictly speaking wrong. We need to limit data in flight. For efficiency
> we should make buffers as large as possible within that limit.

But for latency you should submit URBs as soone as possible within that 
limit, which generally means small buffers.

How about setting the upper limit to URBs in flight based on the baud
rate?  Faster transfers deserve more URBs, right?  Assuming some
minimum number of bytes per URB (4? 8?), there should be enough URBs to
fill a pipeline whose length is around 5 ms or so (interrupt latency).

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/