From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: [PATCH v2 3/3] scsi/ncr5380: Improve interrupt latency during PIO tranfers Date: Wed, 14 Sep 2016 14:12:29 -0400 Message-ID: References: <20160827022959.303563262@telegraphics.com.au> <20160831044453.413698369@telegraphics.com.au> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20160831044453.413698369@telegraphics.com.au> (Finn Thain's message of "Wed, 31 Aug 2016 14:44:56 +1000") Sender: linux-scsi-owner@vger.kernel.org To: Finn Thain Cc: "James E.J. Bottomley" , "Martin K. Petersen" , Geert Uytterhoeven , linux-scsi@vger.kernel.org, linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Schmitz List-Id: linux-m68k@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