From: Valentin Schneider <vschneid@redhat.com>
To: netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Saeed Mahameed <saeedm@nvidia.com>,
Leon Romanovsky <leon@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Yury Norov <yury.norov@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mel Gorman <mgorman@suse.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Heiko Carstens <hca@linux.ibm.com>,
Tony Luck <tony.luck@intel.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Gal Pressman <gal@nvidia.com>, Tariq Toukan <tariqt@nvidia.com>,
Jesse Brandeburg <jesse.brandeburg@intel.com>
Subject: [PATCH v4 6/7] sched/topology: Introduce for_each_numa_hop_cpu()
Date: Fri, 23 Sep 2022 16:55:41 +0100 [thread overview]
Message-ID: <20220923155542.1212814-5-vschneid@redhat.com> (raw)
In-Reply-To: <20220923132527.1001870-1-vschneid@redhat.com>
The recently introduced sched_numa_hop_mask() exposes cpumasks of CPUs
reachable within a given distance budget, but this means each successive
cpumask is a superset of the previous one.
Code wanting to allocate one item per CPU (e.g. IRQs) at increasing
distances would thus need to allocate a temporary cpumask to note which
CPUs have already been visited. This can be prevented by leveraging
for_each_cpu_andnot() - package all that logic into one ugl^D fancy macro.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
include/linux/topology.h | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 3e91ae6d0ad5..7aa7e6a4c739 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -257,5 +257,42 @@ static inline const struct cpumask *sched_numa_hop_mask(int node, int hops)
}
#endif /* CONFIG_NUMA */
+/**
+ * for_each_numa_hop_cpu - iterate over CPUs by increasing NUMA distance,
+ * starting from a given node.
+ * @cpu: the iteration variable.
+ * @node: the NUMA node to start the search from.
+ *
+ * Requires rcu_lock to be held.
+ * Careful: this is a double loop, 'break' won't work as expected.
+ *
+ *
+ * Implementation notes:
+ *
+ * Providing it is valid, the mask returned by
+ * sched_numa_hop_mask(node, hops+1)
+ * is a superset of the one returned by
+ * sched_numa_hop_mask(node, hops)
+ * which may not be that useful for drivers that try to spread things out and
+ * want to visit a CPU not more than once.
+ *
+ * To accommodate for that, we use for_each_cpu_andnot() to iterate over the cpus
+ * of sched_numa_hop_mask(node, hops+1) with the CPUs of
+ * sched_numa_hop_mask(node, hops) removed, IOW we only iterate over CPUs
+ * a given distance away (rather than *up to* a given distance).
+ *
+ * hops=0 forces us to play silly games: we pass cpu_none_mask to
+ * for_each_cpu_andnot(), which turns it into for_each_cpu().
+ */
+#define for_each_numa_hop_cpu(cpu, node) \
+ for (struct { const struct cpumask *curr, *prev; int hops; } __v = \
+ { sched_numa_hop_mask(node, 0), NULL, 0 }; \
+ !IS_ERR_OR_NULL(__v.curr); \
+ __v.hops++, \
+ __v.prev = __v.curr, \
+ __v.curr = sched_numa_hop_mask(node, __v.hops)) \
+ for_each_cpu_andnot(cpu, \
+ __v.curr, \
+ __v.hops ? __v.prev : cpu_none_mask)
#endif /* _LINUX_TOPOLOGY_H */
--
2.31.1
next prev parent reply other threads:[~2022-09-23 15:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 13:25 [PATCH v4 0/7] sched, net: NUMA-aware CPU spreading interface Valentin Schneider
2022-09-23 13:25 ` [PATCH v4 1/7] lib/find_bit: Introduce find_next_andnot_bit() Valentin Schneider
2022-09-23 15:44 ` [PATCH v4 0/7] sched, net: NUMA-aware CPU spreading interface Yury Norov
2022-09-23 15:49 ` Valentin Schneider
2022-09-23 15:55 ` [PATCH v4 2/7] cpumask: Introduce for_each_cpu_andnot() Valentin Schneider
2022-09-25 15:23 ` Yury Norov
2022-09-27 16:45 ` Valentin Schneider
2022-09-27 20:02 ` Yury Norov
2022-09-23 15:55 ` [PATCH v4 3/7] lib/test_cpumask: Add for_each_cpu_and(not) tests Valentin Schneider
2022-09-23 15:55 ` [PATCH v4 4/7] sched/core: Merge cpumask_andnot()+for_each_cpu() into for_each_cpu_andnot() Valentin Schneider
2022-09-23 15:55 ` [PATCH v4 5/7] sched/topology: Introduce sched_numa_hop_mask() Valentin Schneider
2022-09-25 15:00 ` Yury Norov
2022-09-25 15:24 ` Yury Norov
2022-09-27 16:45 ` Valentin Schneider
2022-09-27 19:30 ` Yury Norov
2022-09-25 18:05 ` Yury Norov
2022-09-25 18:13 ` Yury Norov
2022-09-27 16:45 ` Valentin Schneider
2022-09-23 15:55 ` Valentin Schneider [this message]
2022-09-25 14:58 ` [PATCH v4 6/7] sched/topology: Introduce for_each_numa_hop_cpu() Yury Norov
2022-09-27 16:45 ` Valentin Schneider
2022-09-23 15:55 ` [PATCH v4 7/7] net/mlx5e: Improve remote NUMA preferences used for the IRQ affinity hints Valentin Schneider
2022-09-25 7:48 ` [PATCH v4 0/7] sched, net: NUMA-aware CPU spreading interface Tariq Toukan
2022-10-18 6:36 ` Tariq Toukan
2022-10-18 16:50 ` Valentin Schneider
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