From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 9 Mar 2018 09:24:59 +0800 From: Ming Lei To: Thomas Gleixner Cc: Artem Bityutskiy , Jens Axboe , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Laurence Oberman Subject: Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online CPUs as far as possible Message-ID: <20180309012458.GD5228@ming.t460p> References: <20180308105358.1506-1-ming.lei@redhat.com> <1520515113.20980.31.camel@gmail.com> <20180308133440.GA2713@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-ID: Hi Thomas, On Fri, Mar 09, 2018 at 12:20:09AM +0100, Thomas Gleixner wrote: > On Thu, 8 Mar 2018, Ming Lei wrote: > > Actually, it isn't a real fix, the real one is in the following two: > > > > 0c20244d458e scsi: megaraid_sas: fix selection of reply queue > > ed6d043be8cd scsi: hpsa: fix selection of reply queue > > Where are these commits? Neither Linus tree not -next know anything about > them.... Both aren't merged yet, but they should land V4.16, IMO. > > > This patchset can't guarantee that all IRQ vectors are assigned by one > > online CPU, for example, in a quad-socket system, if only one processor > > is present, then some of vectors are still assigned by all offline CPUs, > > and it is a valid case, but still may cause io hang if drivers(hpsa, > > megaraid_sas) select reply queue in current way. > > So my understanding is that these irq patches are enhancements and not bug > fixes. I'll queue them for 4.17 then. Wrt. this IO hang issue, these patches shouldn't be bug fix, but they may fix performance regression[1] for some systems caused by 84676c1f21 ("genirq/affinity: assign vectors to all possible CPUs"). [1] https://marc.info/?l=linux-block&m=152050347831149&w=2 Thanks, Ming