make "nr_cpu_ids" unsigned

PATCH Applied Alexey Dobriyan 1 participant 1 message Aug 19, 2017

Subsystems (11)

Memory management x86 SCSI PowerPC +7 more subsystems

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Alexey Dobriyan

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2017-08-19 11:50 UTC #0 lore raw

PATCH 1/1 make "nr_cpu_ids" unsigned

First, number of CPUs can't be negative number.

Second, different signnnedness leads to suboptimal code in the following cases:

	kmalloc(nr_cpu_ids * sizeof(X));

"int" has to be sign extended to size_t.

2)
while (loff_t *pos < nr_cpu_ids)

MOVSXD is 1 byte longed than the same MOV.

Other cases exist as well. Basically compiler is told that nr_cpu_ids can't be negative which can't be deduced if it is "int".

Code savings on allyesconfig kernel: -3KB

add/remove: 0/0 grow/shrink: 25/264 up/down: 261/-3631 (-3370)
function old new delta
coretemp_cpu_online 450 512 +62
rcu_init_one 1234 1272 +38
pci_device_probe 374 399 +25

...

pgdat_reclaimable_pages 628 556 -72
select_fallback_rq 446 369 -77
task_numa_find_cpu 1923 1807 -116

Signed-off-by Alexey Dobriyan <[email protected]>

---

 arch/arm64/kernel/smp.c              |    2 +-
 arch/powerpc/kernel/paca.c           |    2 +-
 arch/powerpc/kernel/setup-common.c   |    2 +-
 arch/powerpc/sysdev/xive/native.c    |    4 ++--
 arch/tile/kernel/setup.c             |    2 +-
 arch/x86/kernel/apic/apic.c          |    2 +-
 arch/x86/kernel/setup_percpu.c       |    2 +-
 arch/x86/kernel/smpboot.c            |    2 +-
 drivers/base/cpu.c                   |    4 ++--
 drivers/scsi/scsi_debug.c            |    2 +-
 include/linux/cpumask.h              |    6 +++---
 kernel/rcu/tree.c                    |    2 +-
 kernel/rcu/tree_plugin.h             |    2 +-
 kernel/sched/topology.c              |    2 +-
 kernel/smp.c                         |    2 +-
 kernel/trace/trace_functions_graph.c |    2 +-
 mm/slub.c                            |    2 +-
 17 files changed, 21 insertions(+), 21 deletions(-)

arch/arm64/kernel/smp.c +1 -1

@@ -690,7 +690,7 @@ void __init smp_init_cpus(void)
 				      acpi_parse_gic_cpu_interface, 0);
 
 	if (cpu_count > nr_cpu_ids)
-		pr_warn("Number of cores (%d) exceeds configured maximum of %d - clipping\n",
+		pr_warn("Number of cores (%d) exceeds configured maximum of %u - clipping\n",
 			cpu_count, nr_cpu_ids);
 
 	if (!bootcpu_valid) {

arch/powerpc/kernel/paca.c +1 -1

@@ -215,7 +215,7 @@ void __init allocate_pacas(void)
 	paca = __va(memblock_alloc_base(paca_size, PAGE_SIZE, limit));
 	memset(paca, 0, paca_size);
 
-	printk(KERN_DEBUG "Allocated %u bytes for %d pacas at %p\n",
+	printk(KERN_DEBUG "Allocated %u bytes for %u pacas at %p\n",
 		paca_size, nr_cpu_ids, paca);
 
 	allocate_lppacas(nr_cpu_ids, limit);

arch/powerpc/kernel/setup-common.c +1 -1

@@ -551,7 +551,7 @@ void __init smp_setup_cpu_maps(void)
 		if (maxcpus > nr_cpu_ids) {
 			printk(KERN_WARNING
 			       "Partition configured for %d cpus, "
-			       "operating system maximum is %d.\n",
+			       "operating system maximum is %u.\n",
 			       maxcpus, nr_cpu_ids);
 			maxcpus = nr_cpu_ids;
 		} else

arch/powerpc/sysdev/xive/native.c +2 -2

@@ -515,13 +515,13 @@ static bool xive_parse_provisioning(struct device_node *np)
 static void xive_native_setup_pools(void)
 {
 	/* Allocate a pool big enough */
-	pr_debug("XIVE: Allocating VP block for pool size %d\n", nr_cpu_ids);
+	pr_debug("XIVE: Allocating VP block for pool size %u\n", nr_cpu_ids);
 
 	xive_pool_vps = xive_native_alloc_vp_block(nr_cpu_ids);
 	if (WARN_ON(xive_pool_vps == XIVE_INVALID_VP))
 		pr_err("XIVE: Failed to allocate pool VP, KVM might not function\n");
 
-	pr_debug("XIVE: Pool VPs allocated at 0x%x for %d max CPUs\n",
+	pr_debug("XIVE: Pool VPs allocated at 0x%x for %u max CPUs\n",
 		 xive_pool_vps, nr_cpu_ids);
 }

arch/tile/kernel/setup.c +1 -1

@@ -1200,7 +1200,7 @@ static void __init validate_hv(void)
 	 * We use a struct cpumask for this, so it must be big enough.
 	 */
 	if ((smp_height * smp_width) > nr_cpu_ids)
-		early_panic("Hypervisor %d x %d grid too big for Linux NR_CPUS %d\n",
+		early_panic("Hypervisor %d x %d grid too big for Linux NR_CPUS %u\n",
 			    smp_height, smp_width, nr_cpu_ids);
 #endif

arch/x86/kernel/apic/apic.c +1 -1

@@ -2137,7 +2137,7 @@ static int allocate_logical_cpuid(int apicid)
 
 	/* Allocate a new cpuid. */
 	if (nr_logical_cpuids >= nr_cpu_ids) {
-		WARN_ONCE(1, "APIC: NR_CPUS/possible_cpus limit of %i reached. "
+		WARN_ONCE(1, "APIC: NR_CPUS/possible_cpus limit of %u reached. "
 			     "Processor %d/0x%x and the rest are ignored.\n",
 			     nr_cpu_ids, nr_logical_cpuids, apicid);
 		return -EINVAL;

arch/x86/kernel/setup_percpu.c +1 -1

@@ -171,7 +171,7 @@ void __init setup_per_cpu_areas(void)
 	unsigned long delta;
 	int rc;
 
-	pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%d nr_node_ids:%d\n",
+	pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%u nr_node_ids:%d\n",
 		NR_CPUS, nr_cpumask_bits, nr_cpu_ids, nr_node_ids);
 
 	/*

arch/x86/kernel/smpboot.c +1 -1

@@ -1457,7 +1457,7 @@ __init void prefill_possible_map(void)
 
 	/* nr_cpu_ids could be reduced via nr_cpus= */
 	if (possible > nr_cpu_ids) {
-		pr_warn("%d Processors exceeds NR_CPUS limit of %d\n",
+		pr_warn("%d Processors exceeds NR_CPUS limit of %u\n",
 			possible, nr_cpu_ids);
 		possible = nr_cpu_ids;
 	}

drivers/base/cpu.c +2 -2

@@ -256,9 +256,9 @@ static ssize_t print_cpus_offline(struct device *dev,
 			buf[n++] = ',';
 
 		if (nr_cpu_ids == total_cpus-1)
-			n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
+			n += snprintf(&buf[n], len - n, "%u", nr_cpu_ids);
 		else
-			n += snprintf(&buf[n], len - n, "%d-%d",
+			n += snprintf(&buf[n], len - n, "%u-%d",
 						      nr_cpu_ids, total_cpus-1);
 	}

drivers/scsi/scsi_debug.c +1 -1

@@ -5466,7 +5466,7 @@ static int sdebug_driver_probe(struct device * dev)
 		return error;
 	}
 	if (submit_queues > nr_cpu_ids) {
-		pr_warn("%s: trim submit_queues (was %d) to nr_cpu_ids=%d\n",
+		pr_warn("%s: trim submit_queues (was %d) to nr_cpu_ids=%u\n",
 			my_name, submit_queues, nr_cpu_ids);
 		submit_queues = nr_cpu_ids;
 	}

include/linux/cpumask.h +3 -3

@@ -32,15 +32,15 @@ typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;
 #define cpumask_pr_args(maskp)		nr_cpu_ids, cpumask_bits(maskp)
 
 #if NR_CPUS == 1
-#define nr_cpu_ids		1
+#define nr_cpu_ids		1U
 #else
-extern int nr_cpu_ids;
+extern unsigned int nr_cpu_ids;
 #endif
 
 #ifdef CONFIG_CPUMASK_OFFSTACK
 /* Assuming NR_CPUS is huge, a runtime limit is more efficient.  Also,
  * not all bits may be allocated. */
-#define nr_cpumask_bits	((unsigned int)nr_cpu_ids)
+#define nr_cpumask_bits	nr_cpu_ids
 #else
 #define nr_cpumask_bits	((unsigned int)NR_CPUS)
 #endif

kernel/rcu/tree.c +1 -1

@@ -4134,7 +4134,7 @@ static void __init rcu_init_geometry(void)
 	if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
 	    nr_cpu_ids == NR_CPUS)
 		return;
-	pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
+	pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
 		rcu_fanout_leaf, nr_cpu_ids);
 
 	/*

kernel/rcu/tree_plugin.h +1 -1

@@ -89,7 +89,7 @@ static void __init rcu_bootup_announce_oddness(void)
 	if (rcu_fanout_leaf != RCU_FANOUT_LEAF)
 		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
 	if (nr_cpu_ids != NR_CPUS)
-		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
+		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids);
 #ifdef CONFIG_RCU_BOOST
 	pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", kthread_prio, CONFIG_RCU_BOOST_DELAY);
 #endif

kernel/sched/topology.c +1 -1

@@ -476,7 +476,7 @@ static int __init isolated_cpu_setup(char *str)
 	alloc_bootmem_cpumask_var(&cpu_isolated_map);
 	ret = cpulist_parse(str, cpu_isolated_map);
 	if (ret) {
-		pr_err("sched: Error, all isolcpus= values must be between 0 and %d\n", nr_cpu_ids);
+		pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n", nr_cpu_ids);
 		return 0;
 	}
 	return 1;

kernel/smp.c +1 -1

@@ -548,7 +548,7 @@ static int __init maxcpus(char *str)
 early_param("maxcpus", maxcpus);
 
 /* Setup number of possible processor ids */
-int nr_cpu_ids __read_mostly = NR_CPUS;
+unsigned int nr_cpu_ids __read_mostly = NR_CPUS;
 EXPORT_SYMBOL(nr_cpu_ids);
 
 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */

kernel/trace/trace_functions_graph.c +1 -1

@@ -1543,7 +1543,7 @@ fs_initcall(init_graph_tracefs);
 
 static __init int init_graph_trace(void)
 {
-	max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);
+	max_bytes_for_cpu = snprintf(NULL, 0, "%u", nr_cpu_ids - 1);
 
 	if (!register_trace_event(&graph_trace_entry_event)) {
 		pr_warn("Warning: could not register graph trace events\n");

mm/slub.c +1 -1

@@ -4196,7 +4196,7 @@ void __init kmem_cache_init(void)
 	cpuhp_setup_state_nocalls(CPUHP_SLUB_DEAD, "slub:dead", NULL,
 				  slub_cpu_dead);
 
-	pr_info("SLUB: HWalign=%d, Order=%d-%d, MinObjects=%d, CPUs=%d, Nodes=%d\n",
+	pr_info("SLUB: HWalign=%d, Order=%d-%d, MinObjects=%d, CPUs=%u, Nodes=%d\n",
 		cache_line_size(),
 		slub_min_order, slub_max_order, slub_min_objects,
 		nr_cpu_ids, nr_node_ids);