From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Smart Subject: Re: [PATCH v2 12/20] lpfc: Limit amount of work processed in IRQ Date: Mon, 7 Aug 2017 13:50:59 -0700 Message-ID: <389dd23c-6cc4-8498-5980-9fdd0610b516@gmail.com> References: <20170805004731.1335-1-jsmart2021@gmail.com> <20170805004731.1335-13-jsmart2021@gmail.com> <20170807084354.GO3978@linux-x5ow.site> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-qk0-f195.google.com ([209.85.220.195]:33148 "EHLO mail-qk0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662AbdHGUvE (ORCPT ); Mon, 7 Aug 2017 16:51:04 -0400 Received: by mail-qk0-f195.google.com with SMTP id d145so1605630qkc.0 for ; Mon, 07 Aug 2017 13:51:04 -0700 (PDT) In-Reply-To: <20170807084354.GO3978@linux-x5ow.site> Content-Language: en-US Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Johannes Thumshirn Cc: linux-scsi@vger.kernel.org, Dick Kennedy , James Smart On 8/7/2017 1:43 AM, Johannes Thumshirn wrote: > On Fri, Aug 04, 2017 at 05:47:23PM -0700, James Smart wrote: >> From: Dick Kennedy >> >> Various oops being seen on being in the ISR too long and cpu >> lockups, when under heavy load. >> >> The amount of work being posted off of completion queues kept >> the ISR running almost all the time >> >> Correct the issue by limiting the amount of work per itteration. > > Have you considered using the IRQ poll mechanism for this? It deferres the > heavy lifing into the Soft-IRQ layer and this could help you a lot here. IIRC > I've sent James the "Slides" from my LSF/MM session which have the function > protoypes on 'em. See 'lib/irq_poll.c' or the be2iscsi driver for further > details. We considered it, so far declined it - preferring the behavior of the dynamic hw coalescing we have. That said, we're already considering the softirq approach, which shouldn't be that large of a delta. However, we've chosen to delay that change while we harden the overall stability. -- james