Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755850Ab3E0RNp (ORCPT ); Mon, 27 May 2013 13:13:45 -0400 Received: from mail-la0-f49.google.com ([209.85.215.49]:38135 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755710Ab3E0RNm (ORCPT ); Mon, 27 May 2013 13:13:42 -0400 Message-ID: <51A39441.9000609@cogentembedded.com> Date: Mon, 27 May 2013 21:13:37 +0400 From: Sergei Shtylyov User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Ming Lei CC: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Alan Stern Subject: Re: [PATCH 2/2] USB: hcd: only unmap the actual completed DMA buffer References: <1369671187-24430-1-git-send-email-ming.lei@canonical.com> <1369671187-24430-3-git-send-email-ming.lei@canonical.com> In-Reply-To: <1369671187-24430-3-git-send-email-ming.lei@canonical.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1322 Lines: 40 Hello. On 27-05-2013 20:13, Ming Lei wrote: > This patch only unmap the actual completed DMA buffer instead of > the whole transfer buffer. Who will unmap the rest of the buffer? > It is common to see only part of DMA transfer is completed, especially > in case of DMA_FROM_DEVICE because the length of incoming traffic often > is unknown before submitting URB, so this patch may improve USB > DMA unmapping which runs in hard irq context. > The patch has been tested on ARMv7(Pandaboard), and it is observed that > at average ~25us is saved about ehci interrupt handling on below usbnet > test case: > - Pandaboard: IP address is IP_A > - on one x86 box, run below command: > #ping -f -s 1472 IP_A > - compute ehci interrupt handling time on Pandaboard during ping > test This seems just crazy to me. What has been mapped, should be unmapped. > Cc: Alan Stern > Signed-off-by: Ming Lei > --- > drivers/usb/core/hcd.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) WBR, Sergei -- 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/