From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758873AbcINSMn (ORCPT ); Wed, 14 Sep 2016 14:12:43 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:36040 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbcINSMk (ORCPT ); Wed, 14 Sep 2016 14:12:40 -0400 To: Finn Thain Cc: "James E.J. Bottomley" , "Martin K. Petersen" , Geert Uytterhoeven , , , , Michael Schmitz Subject: Re: [PATCH v2 3/3] scsi/ncr5380: Improve interrupt latency during PIO tranfers From: "Martin K. Petersen" Organization: Oracle Corporation References: <20160827022959.303563262@telegraphics.com.au> <20160831044453.413698369@telegraphics.com.au> Date: Wed, 14 Sep 2016 14:12:29 -0400 In-Reply-To: <20160831044453.413698369@telegraphics.com.au> (Finn Thain's message of "Wed, 31 Aug 2016 14:44:56 +1000") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Finn" == Finn Thain writes: Finn> Large PIO transfers are broken up into chunks to try to avoid Finn> disabling local IRQs for long periods. But IRQs are still disabled Finn> for too long and this causes SCC FIFO overruns during serial port Finn> transfers. Finn> This patch reduces the PIO chunk size to reduce interrupt latency Finn> to something on the order of milliseconds, at the expense of Finn> additional CPU overhead from extra iterations of the Finn> NCR5380_main() loop. Applied to 4.9/scsi-queue. -- Martin K. Petersen Oracle Linux Engineering