Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965542AbdGTS4B (ORCPT ); Thu, 20 Jul 2017 14:56:01 -0400 Received: from relay1.sgi.com ([192.48.180.66]:57040 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934563AbdGTS4A (ORCPT ); Thu, 20 Jul 2017 14:56:00 -0400 X-Greylist: delayed 340 seconds by postgrey-1.27 at vger.kernel.org; Thu, 20 Jul 2017 14:56:00 EDT Date: Thu, 20 Jul 2017 13:50:20 -0500 From: Andrew Banman To: Ingo Molnar Cc: Andrew Banman , mingo@redhat.com, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, rja@hpe.com, mike.travis@hpe.com Subject: Re: [PATCH] x86/platform/uv/BAU: disable BAU on single hub configurations Message-ID: <20170720185020.GK277355@stormcage.americas.sgi.com> References: <1500414693-84043-1-git-send-email-abanman@hpe.com> <20170720114750.mykc2i2cc44m34sp@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170720114750.mykc2i2cc44m34sp@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2570 Lines: 91 On Thu, Jul 20, 2017 at 01:47:50PM +0200, Ingo Molnar wrote: > > * Andrew Banman wrote: > > > The BAU confers no benefit to a UV system running with only one hub/socket. > > Permanently disable the BAU driver if there are less than two hubs online > > to avoid BAU overhead. We have observed failed boots on single-socket UV4 > > systems caused by BAU that are avoided with this patch. > > > > Signed-off-by: Andrew Banman > > Acked-by: Russ Anderson > > Acked-by: Mike Travis > > --- > > arch/x86/platform/uv/tlb_uv.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c > > index 2511a28..88216cc 100644 > > --- a/arch/x86/platform/uv/tlb_uv.c > > +++ b/arch/x86/platform/uv/tlb_uv.c > > @@ -2251,6 +2251,12 @@ static int __init uv_bau_init(void) > > } > > > > nuvhubs = uv_num_possible_blades(); > > + if (nuvhubs < 2) { > > + pr_crit("UV: BAU disabled - insufficient hub count\n"); > > + set_bau_off(); > > + nobau_perm = 1; > > + return 0; > > + } > > Yeah, could you structure the error paths in this function in a bit more organized > fashion? It has two similar error handling blocks: > > > pr_crit("UV: BAU disabled - insufficient hub count\n"); > set_bau_off(); > nobau_perm = 1; > return 0; > > ... > > set_bau_off(); > nobau_perm = 1; > return 0; > > which could be consolidated via the usual goto exception construct: > > if (nuvhubs < 2) { > pr_crit("UV: BAU disabled - insufficient hub count\n"); > goto err_disable_bau; > } > ... > > if (init_per_cpu(nuvhubs, uv_base_pnode)) > pr_crit("UV: BAU disabled - per CPU init failed\n"); > goto err_disable_bau; > } > > ... > return 0; > > err_disable_bau: > > set_bau_off(); > nobau_perm = 1; > return 0; > > Note that I added an error message to the second case as well. > > Plus, in the error case you might want to use a 'return -EINVAL;' instead of > return 0, or so? I agree with your suggestions, and I'm happy to make the changes. > > Plus plus, there's probably a (mild) memory leak in the error paths, can the > cpumasks be free_cpumask_var() freed - or are they still required even if BAU is > disabled? In the case of nobau_perm=1 they can be freed. I will include that in the next version. > > Thanks, > > Ingo Thank you! I'll have the next version out shortly. Andrew