From: Valentin Schneider <vschneid@redhat.com>
To: Yury Norov <yury.norov@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org, Saeed Mahameed <saeedm@nvidia.com>,
Pawel Chmielewski <pawel.chmielewski@intel.com>,
Leon Romanovsky <leon@kernel.org>,
"David S. 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>,
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: Re: [PATCH v2 2/8] sched/topology: introduce sched_numa_find_next_cpu()
Date: Wed, 26 Apr 2023 10:17:12 +0100 [thread overview]
Message-ID: <xhsmhwn1zj947.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <ZEi1/zO9cGccogea@yury-ThinkPad>
On 25/04/23 22:26, Yury Norov wrote:
> On Tue, Apr 25, 2023 at 10:54:56AM +0100, Valentin Schneider wrote:
>> On 19/04/23 22:19, Yury Norov wrote:
>> > +/*
>> > + * sched_numa_find_next_cpu() - given the NUMA topology, find the next cpu
>> > + * cpumask: cpumask to find a cpu from
>> > + * cpu: current cpu
>> > + * node: local node
>> > + * hop: (in/out) indicates distance order of current CPU to a local node
>> > + *
>> > + * The function searches for next cpu at a given NUMA distance, indicated
>> > + * by hop, and if nothing found, tries to find CPUs at a greater distance,
>> > + * starting from the beginning.
>> > + *
>> > + * Return: cpu, or >= nr_cpu_ids when nothing found.
>> > + */
>> > +int sched_numa_find_next_cpu(const struct cpumask *cpus, int cpu, int node, unsigned int *hop)
>> > +{
>> > + unsigned long *cur, *prev;
>> > + struct cpumask ***masks;
>> > + unsigned int ret;
>> > +
>> > + if (*hop >= sched_domains_numa_levels)
>> > + return nr_cpu_ids;
>> > +
>> > + masks = rcu_dereference(sched_domains_numa_masks);
>> > + cur = cpumask_bits(masks[*hop][node]);
>> > + if (*hop == 0)
>> > + ret = find_next_and_bit(cpumask_bits(cpus), cur, nr_cpu_ids, cpu);
>> > + else {
>> > + prev = cpumask_bits(masks[*hop - 1][node]);
>> > + ret = find_next_and_andnot_bit(cpumask_bits(cpus), cur, prev, nr_cpu_ids, cpu);
>> > + }
>> > +
>> > + if (ret < nr_cpu_ids)
>> > + return ret;
>> > +
>> > + *hop += 1;
>> > + return sched_numa_find_next_cpu(cpus, 0, node, hop);
>>
>> sched_domains_numa_levels is a fairly small number, so the recursion depth
>> isn't something we really need to worry about - still, the iterative
>> variant of this is fairly straightforward to get to:
>
> This is a tail recursion. Compiler normally converts it into the loop just
> as well. At least, my GCC does.
I'd hope so in 2023! I still prefer the iterative approach as I find it
more readable, but I'm not /too/ strongly attached to it.
next prev parent reply other threads:[~2023-04-26 9:20 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-20 5:19 [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro Yury Norov
2023-04-20 5:19 ` [PATCH v2 1/8] lib/find: add find_next_and_andnot_bit() Yury Norov
2023-04-20 5:19 ` [PATCH v2 2/8] sched/topology: introduce sched_numa_find_next_cpu() Yury Norov
2023-04-25 9:54 ` Valentin Schneider
2023-04-26 5:26 ` Yury Norov
2023-04-26 9:17 ` Valentin Schneider [this message]
2023-04-20 5:19 ` [PATCH v2 3/8] sched/topology: add for_each_numa_cpu() macro Yury Norov
2023-04-25 9:54 ` Valentin Schneider
2023-04-26 5:32 ` Yury Norov
2023-04-26 9:17 ` Valentin Schneider
2023-04-20 5:19 ` [PATCH v2 4/8] net: mlx5: switch comp_irqs_request() to using for_each_numa_cpu Yury Norov
2023-04-20 8:27 ` Tariq Toukan
2023-04-20 22:45 ` Yury Norov
2023-04-20 5:19 ` [PATCH v2 5/8] lib/cpumask: update comment to cpumask_local_spread() Yury Norov
2023-04-20 5:19 ` [PATCH v2 6/8] sched/topology: export sched_domains_numa_levels Yury Norov
2023-04-20 5:19 ` [PATCH v2 7/8] lib: add test for for_each_numa_{cpu,hop_mask}() Yury Norov
2023-04-24 17:09 ` Valentin Schneider
2023-04-26 5:50 ` Yury Norov
2023-04-26 9:17 ` Valentin Schneider
2023-04-26 20:51 ` Yury Norov
2023-04-27 9:35 ` Valentin Schneider
2023-04-20 5:19 ` [PATCH v2 8/8] sched: drop for_each_numa_hop_mask() Yury Norov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=xhsmhwn1zj947.mognet@vschneid.remote.csb \
--to=vschneid@redhat.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=baohua@kernel.org \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=davem@davemloft.net \
--cc=dietmar.eggemann@arm.com \
--cc=edumazet@google.com \
--cc=gal@nvidia.com \
--cc=gregkh@linuxfoundation.org \
--cc=hca@linux.ibm.com \
--cc=juri.lelli@redhat.com \
--cc=kuba@kernel.org \
--cc=leon@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=pawel.chmielewski@intel.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=saeedm@nvidia.com \
--cc=tariqt@nvidia.com \
--cc=vincent.guittot@linaro.org \
--cc=yury.norov@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).