linux-kernel - [RFC Patch V1 27/30] x86, numa: Kill useless code to improve code readability

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Message-Id: <1405064267-11678-28-git-send-email-jiang.liu@linux.intel.com>
Date:	Fri, 11 Jul 2014 15:37:44 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Tang Chen <tangchen@...fujitsu.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Lans Zhang <jia.zhang@...driver.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	Tony Luck <tony.luck@...el.com>, linux-mm@...ck.org,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: [RFC Patch V1 27/30] x86, numa: Kill useless code to improve code readability

According to x86 boot sequence, early_cpu_to_node() always returns
NUMA_NO_NODE when called from numa_init(). So kill useless code
to improve code readability.

Related code sequence as below:
x86_cpu_to_node_map is set until step 2, so it is still the default
value (NUMA_NO_NODE) when accessed at step 1.

start_kernel()
	setup_arch()
		initmem_init()
			x86_numa_init()
				numa_init()
					early_cpu_to_node()
1)						return early_per_cpu_ptr(x86_cpu_to_node_map)[cpu];
		acpi_boot_init();
		sfi_init()
		x86_dtb_init()
			generic_processor_info()
				early_per_cpu(x86_cpu_to_apicid, cpu) = apicid;
		init_cpu_to_node()
			numa_set_node(cpu, node);
2)				per_cpu(x86_cpu_to_node_map, cpu) = node;

	rest_init()
		kernel_init()
			smp_init()
				native_cpu_up()
					start_secondary()
						numa_set_node()
							per_cpu(x86_cpu_to_node_map, cpu) = node;

Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
---
 arch/x86/mm/numa.c |   10 ----------
 1 file changed, 10 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index a32b706c401a..eec4f6c322bb 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -545,8 +545,6 @@ static void __init numa_init_array(void)
 
 	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(rr, node_online_map);
 		if (rr == MAX_NUMNODES)
@@ -633,14 +631,6 @@ static int __init numa_init(int (*init_func)(void))
 	if (ret < 0)
 		return ret;
 
-	for (i = 0; i < nr_cpu_ids; i++) {
-		int nid = early_cpu_to_node(i);
-
-		if (nid == NUMA_NO_NODE)
-			continue;
-		if (!node_online(nid))
-			numa_clear_node(i);
-	}
 	numa_init_array();
 
 	/*
-- 
1.7.10.4

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