linux-kernel - Re: USB performance bug since kernel 2.6.13 (CRITICAL???)

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Date:	Thu, 12 Oct 2006 15:55:55 -0400
From:	Lee Revell <rlrevell@...-job.com>
To:	Open Source <opensource3141@...oo.com>
Cc:	linux-usb-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: USB performance bug since kernel 2.6.13 (CRITICAL???)

On Thu, 2006-10-12 at 12:33 -0700, Open Source wrote:
> I am using a device that submits URBs asynchronously using the libusb
> devio infrastructure.  In version 2.6.12 I am able to submit and reap
> URBs for my particular application at a transaction rate of one per
> millisecond.  A transaction consists of a single WRITE URB (< 512
> bytes) followed by a single READ URB (1024 bytes).  Once I upgrade to
> version 2.6.13, the transactional rate drops to one per 4
> milliseconds!

The kernel's internal tick rate was lowered from 1000Hz to 250Hz
starting with 2.6.13.  Rebuild with CONFIG_HZ=1000 and the performance
should return to normal.

Lee

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