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Date:   Fri, 11 Nov 2022 08:25:51 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Yury Norov <yury.norov@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Barry Song <baohua@kernel.org>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Gal Pressman <gal@nvidia.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Heiko Carstens <hca@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Mel Gorman <mgorman@suse.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Saeed Mahameed <saeedm@nvidia.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Tariq Toukan <tariqt@nvidia.com>,
        Tariq Toukan <ttoukan.linux@gmail.com>,
        Tony Luck <tony.luck@intel.com>,
        Valentin Schneider <vschneid@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-crypto@vger.kernel.org, netdev@vger.kernel.org,
        linux-rdma@vger.kernel.org
Subject: Re: [PATCH 0/4] cpumask: improve on cpumask_local_spread() locality
Message-ID: <20221111082551.7e71fbf4@kernel.org>
In-Reply-To: <20221111040027.621646-1-yury.norov@gmail.com>
References: <20221111040027.621646-1-yury.norov@gmail.com>
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On Thu, 10 Nov 2022 20:00:23 -0800 Yury Norov wrote:
> cpumask_local_spread() currently checks local node for presence of i'th
> CPU, and then if it finds nothing makes a flat search among all non-local
> CPUs. We can do it better by checking CPUs per NUMA hops.

Nice.

> This series is inspired by Valentin Schneider's "net/mlx5e: Improve remote
> NUMA preferences used for the IRQ affinity hints"
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20220728191203.4055-3-tariqt@nvidia.com/
> 
> According to Valentin's measurements, for mlx5e:
> 
> 	Bottleneck in RX side is released, reached linerate (~1.8x speedup).
> 	~30% less cpu util on TX.
> 
> This patch makes cpumask_local_spread() traversing CPUs based on NUMA
> distance, just as well, and I expect comparabale improvement for its
> users, as in Valentin's case.
> 
> I tested it on my VM with the following NUMA configuration:

nit: the authorship is a bit more complicated, it'd be good to mention
Tariq. Both for the code and attribution of the testing / measurements.