Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422713AbWJNQdo (ORCPT ); Sat, 14 Oct 2006 12:33:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422714AbWJNQdo (ORCPT ); Sat, 14 Oct 2006 12:33:44 -0400 Received: from web58114.mail.re3.yahoo.com ([68.142.236.137]:58019 "HELO web58114.mail.re3.yahoo.com") by vger.kernel.org with SMTP id S1422713AbWJNQdn convert rfc822-to-8bit (ORCPT ); Sat, 14 Oct 2006 12:33:43 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Received:Date:From:Subject:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding; b=3o36vkCmO5QFtQDR8gA/WeVRdJjt7/UVo97UebKEEWd073nfj6KIzyBgStfbaPZDVGjKH8jJcKIkS5hmGfUVkvsRx2s0XXerGeqOzsauCobMa5SniPvdHge7CKXlzpkOxbMcyXeWjRjYDmM8wmOSDx17n5pFYI6mnmSnkf9ZnYs= ; Message-ID: <20061014163342.36731.qmail@web58114.mail.re3.yahoo.com> Date: Sat, 14 Oct 2006 09:33:42 -0700 (PDT) From: Open Source Subject: Re: USB performance bug since kernel 2.6.13 (CRITICAL???) To: Alan Stern Cc: Alan Cox , USB development list , Kernel development list MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1800 Lines: 49 Hi all, Yes, I am on board with both Alans. I did not know about this very nifty option in strace. I will look into it in detail on Mon/Tue and report back. Clearly something is weird, because there are no other load-intensive processes running on the system. I would think that the scheduler would wake up any blocked processes rather than sitting idle for 4 ms. In any case, I am open to the fact it may not be USB per se. We'll see what strace says. As always, thanks for the suggestions. Stay tuned.... ----- Original Message ---- From: Alan Stern To: Open Source Cc: Alan Cox ; USB development list ; Kernel development list Sent: Friday, October 13, 2006 7:11:39 PM Subject: Re: [linux-usb-devel] USB performance bug since kernel 2.6.13 (CRITICAL???) On Sat, 14 Oct 2006, Alan Cox wrote: > Ar Gwe, 2006-10-13 am 16:30 -0700, ysgrifennodd Open Source: > > There is an ioctl that is waiting for the URB to be reaped. > > I am almost certain it is this syscall that is taking 4 ms (as > > opposed to 1 ms with CONFIG_HZ=1000). > > What does strace say about it ? This is measurable not speculation. I completely agree with the other Alan. You don't have to guess about these things. Use strace to see what your process is doing and at the same time use usbmon to see what the USB stack is doing. Run the experiment at both 1000 Hz and 250 Hz and compare the results. Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/