From: Pingfan Liu <kernelfans@gmail.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: x86@kernel.org, linux-mm@kvack.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andy Lutomirski <luto@kernel.org>,
Andi Kleen <ak@linux.intel.com>, Petr Tesarik <ptesarik@suse.cz>,
Michal Hocko <mhocko@suse.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Jonathan Corbet <corbet@lwn.net>,
Nicholas Piggin <npiggin@gmail.com>,
Daniel Vacek <neelx@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/6] x86/numa: define numa_init_array() conditional on CONFIG_NUMA
Date: Tue, 26 Feb 2019 13:40:15 +0800 [thread overview]
Message-ID: <CAFgQCTsOqnBdiFHbFVRsjbPkMuV+egUU7RZ-OoXRLndwJAFjoA@mail.gmail.com> (raw)
In-Reply-To: <8f703c5f-44c7-3a96-487e-3bdf46ee41b0@intel.com>
On Mon, Feb 25, 2019 at 11:24 PM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 2/24/19 4:34 AM, Pingfan Liu wrote:
> > +#ifdef CONFIG_NUMA
> > /*
> > * There are unfortunately some poorly designed mainboards around that
> > * only connect memory to a single CPU. This breaks the 1:1 cpu->node
> > @@ -618,6 +619,9 @@ static void __init numa_init_array(void)
> > rr = next_node_in(rr, node_online_map);
> > }
> > }
> > +#else
> > +static void __init numa_init_array(void) {}
> > +#endif
>
> What functional effect does this #ifdef have?
>
> Let's look at the code:
>
> > static void __init numa_init_array(void)
> > {
> > int rr, i;
> >
> > rr = first_node(node_online_map);
> > for (i = 0; i < nr_cpu_ids; i++) {
> > if (early_cpu_to_node(i) != NUMA_NO_NODE)
> > continue;
> > numa_set_node(i, rr);
> > rr = next_node_in(rr, node_online_map);
> > }
> > }
>
> and "play compiler" for a bit.
>
> The first iteration will see early_cpu_to_node(i)==1 because:
>
> static inline int early_cpu_to_node(int cpu)
> {
> return 0;
> }
>
> if CONFIG_NUMA=n.
>
> In other words, I'm not sure this patch does *anything*.
I had thought separating [3/6] and [4/6] can ease the review. And I
will merge them in next version.
Thanks and regards,
Pingfan
next prev parent reply other threads:[~2019-02-26 5:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-24 12:34 [PATCH 0/6] make memblock allocator utilize the node's fallback info Pingfan Liu
2019-02-24 12:34 ` [PATCH 1/6] mm/numa: extract the code of building node fall back list Pingfan Liu
2019-02-24 12:34 ` [PATCH 2/6] mm/memblock: make full utilization of numa info Pingfan Liu
2019-02-25 7:07 ` kbuild test robot
2019-02-25 7:59 ` kbuild test robot
2019-02-25 15:34 ` Dave Hansen
2019-02-26 5:40 ` Pingfan Liu
2019-02-26 12:37 ` Dave Hansen
2019-02-26 11:58 ` Mike Rapoport
2019-02-27 9:23 ` Pingfan Liu
2019-02-24 12:34 ` [PATCH 3/6] x86/numa: define numa_init_array() conditional on CONFIG_NUMA Pingfan Liu
2019-02-25 15:23 ` Dave Hansen
2019-02-26 5:40 ` Pingfan Liu [this message]
2019-02-24 12:34 ` [PATCH 4/6] x86/numa: concentrate the code of setting cpu to node map Pingfan Liu
2019-02-24 12:34 ` [PATCH 5/6] x86/numa: push forward the setup of node to cpumask map Pingfan Liu
2019-02-25 15:30 ` Dave Hansen
2019-02-26 5:40 ` Pingfan Liu
2019-02-24 12:34 ` [PATCH 6/6] x86/numa: build node fallback info after setting up " Pingfan Liu
2019-02-25 16:03 ` [PATCH 0/6] make memblock allocator utilize the node's fallback info Michal Hocko
2019-02-26 5:47 ` Pingfan Liu
2019-02-26 12:09 ` Michal Hocko
2019-03-05 12:37 ` Pingfan Liu
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