From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kashyap Desai Subject: RE: [RFC 0/2] mpt3sas/megaraid_sas : irq poll and load balancing of reply queue Date: Mon, 22 Jan 2018 17:03:15 +0530 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Received: from mail-io0-f178.google.com ([209.85.223.178]:43801 "EHLO mail-io0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751086AbeAVLdT (ORCPT ); Mon, 22 Jan 2018 06:33:19 -0500 Received: by mail-io0-f178.google.com with SMTP id 72so9089129iom.10 for ; Mon, 22 Jan 2018 03:33:19 -0800 (PST) References: 92d894a263bf37152fdae9699ccaccff@mail.gmail.com In-Reply-To: 92d894a263bf37152fdae9699ccaccff@mail.gmail.com Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org, Peter Rivera > > In Summary, > CPU completing IO which is not contributing to IO submission, may cause cpu > lockup. > If CPUs count to MSI-X vector count ratio is X:1 (where X > 1) then using irq poll > interface, we can avoid the CPU lockups and by equally distributing the > interrupts among the enabled MSI-x interrupts we can avoid performance > issues. > > We are planning to use both the fixes only if cpu count is more than FW > supported MSI-x vector. > Please review and provide your feedback. I have appended both the patches. Hi - Assuming method explained here is in-line with Linux SCSI subsystem and there is no better method to fix such issue. I am planning to provide the same solution for internal testing and maintainers of respective driver (mpt3sas and megaraid_sas) will post final patch to the upstream based on results. As of now PoC results looks promising with the above mentioned solution and no cpu lock was discovered. > > Thanks, Kashyap > >