Message ID | 20230430171809.124686-5-yury.norov@gmail.com |
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State | New |
Headers |
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Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Steven Rostedt <rostedt@goodmis.org>, Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>, Daniel Bristot de Oliveira <bristot@redhat.com>, Valentin Schneider <vschneid@redhat.com>, Tariq Toukan <tariqt@nvidia.com>, Gal Pressman <gal@nvidia.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Heiko Carstens <hca@linux.ibm.com>, Barry Song <baohua@kernel.org> Subject: [PATCH v3 4/8] sched/topology: add for_each_numa_{,online}_cpu() macro Date: Sun, 30 Apr 2023 10:18:05 -0700 Message-Id: <20230430171809.124686-5-yury.norov@gmail.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230430171809.124686-1-yury.norov@gmail.com> References: <20230430171809.124686-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1764623007506812289?= X-GMAIL-MSGID: =?utf-8?q?1764623007506812289?= |
Series |
sched/topology: add for_each_numa_cpu() macro
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Commit Message
Yury Norov
April 30, 2023, 5:18 p.m. UTC
for_each_cpu() is widely used in the kernel, and it's beneficial to
create a NUMA-aware version of the macro.
Recently added for_each_numa_hop_mask() works, but switching existing
codebase to using it is not an easy process.
New for_each_numa_cpu() is designed to be similar to the for_each_cpu().
It allows to convert existing code to NUMA-aware as simple as adding a
hop iterator variable and passing it inside new macro. for_each_numa_cpu()
takes care of the rest.
At the moment, we have 2 users of NUMA-aware enumerators. One is
Melanox's in-tree driver, and another is Intel's in-review driver:
https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/
Both real-life examples follow the same pattern:
for_each_numa_hop_mask(cpus, prev, node) {
for_each_cpu_andnot(cpu, cpus, prev) {
if (cnt++ == max_num)
goto out;
do_something(cpu);
}
prev = cpus;
}
With the new macro, it would look like this:
for_each_numa_online_cpu(cpu, hop, node) {
if (cnt++ == max_num)
break;
do_something(cpu);
}
Straight conversion of existing for_each_cpu() codebase to NUMA-aware
version with for_each_numa_hop_mask() is difficult because it doesn't
take a user-provided cpu mask, and eventually ends up with open-coded
double loop. With for_each_numa_cpu() it shouldn't be a brainteaser.
Consider the NUMA-ignorant example:
cpumask_t cpus = get_mask();
int cnt = 0, cpu;
for_each_cpu(cpu, cpus) {
if (cnt++ == max_num)
break;
do_something(cpu);
}
Converting it to NUMA-aware version would be as simple as:
cpumask_t cpus = get_mask();
int node = get_node();
int cnt = 0, hop, cpu;
for_each_numa_cpu(cpu, hop, node, cpus) {
if (cnt++ == max_num)
break;
do_something(cpu);
}
The latter looks more verbose and avoids from open-coding that annoying
double loop. Another advantage is that it works with a 'hop' parameter with
the clear meaning of NUMA distance, and doesn't make people not familiar
to enumerator internals bothering with current and previous masks machinery.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
include/linux/topology.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/include/linux/topology.h b/include/linux/topology.h index da92fea38585..6ed01962878c 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -291,4 +291,23 @@ sched_numa_hop_mask(unsigned int node, unsigned int hops) !IS_ERR_OR_NULL(mask); \ __hops++) +/** + * for_each_numa_cpu - iterate over cpus in increasing order taking into account + * NUMA distances from a given node. + * @cpu: the (optionally unsigned) integer iterator + * @hop: the iterator variable, must be initialized to a desired minimal hop. + * @node: the NUMA node to start the search from. + * @mask: the cpumask pointer + * + * Requires rcu_lock to be held. + */ +#define for_each_numa_cpu(cpu, hop, node, mask) \ + for ((cpu) = 0, (hop) = 0; \ + (cpu) = sched_numa_find_next_cpu((mask), (cpu), (node), &(hop)),\ + (cpu) < nr_cpu_ids; \ + (cpu)++) + +#define for_each_numa_online_cpu(cpu, hop, node) \ + for_each_numa_cpu(cpu, hop, node, cpu_online_mask) + #endif /* _LINUX_TOPOLOGY_H */