Re: [PATCH 01/10] x86: Change size of APICIDs from u8 to u16

[Mike Travis <travis@sgi.com>]

Mel Gorman wrote:
> On (13/01/08 10:34), travis@sgi.com didst pronounce:
>> Change the size of APICIDs from u8 to u16.  This partially
>> supports the new x2apic mode that will be present on future
>> processor chips. (Chips actually support 32-bit APICIDs, but that
>> change is more intrusive. Supporting 16-bit is sufficient for now).
>>
>> Signed-off-by: Jack Steiner <steiner@sgi.com>
>>
>> I've included just the partial change from u8 to u16 apicids.  The
>> remaining x2apic changes will be in a separate patch.
>>
>> In addition, the fake_node_to_pxm_map[] and fake_apicid_to_node[]
>> tables have been moved from local data to the __initdata section
>> reducing stack pressure when MAX_NUMNODES and MAX_LOCAL_APIC are
>> increased in size.
>>
> 
> Does this make a different to inter-node effects?

Are you asking about the movement of the fake arrays?  Since these
are used once and discarded, the it shouldn't have any effect.

If you are asking abut the general increase to 16 bits, I don't
think we have much choice.  The hardware for 16 (and as mentioned
32) is coming.  I'm trying to minimize as much traffic between
node 0 and the other nodes.  Apic id AFAICT is used mostly for
sending IPI's, either to cpus within the node or to remote cpus.
Using the remote cpu's node memory to query it's apicid seems
reasonable?  And, of course, having all the data about one's own
node local to itself seems a big win as well.

Thanks,
Mike

> 
>> Signed-off-by: Mike Travis <travis@sgi.com>
>> Reviewed-by: Christoph Lameter <clameter@sgi.com>
>> ---
>>  arch/x86/kernel/genapic_64.c |    4 ++--
>>  arch/x86/kernel/mpparse_64.c |    4 ++--
>>  arch/x86/kernel/smpboot_64.c |    2 +-
>>  arch/x86/mm/numa_64.c        |    2 +-
>>  arch/x86/mm/srat_64.c        |   22 +++++++++++++---------
>>  include/asm-x86/processor.h  |   14 +++++++-------
>>  include/asm-x86/smp_64.h     |    8 ++++----
>>  7 files changed, 30 insertions(+), 26 deletions(-)
>>
>> --- a/arch/x86/kernel/genapic_64.c
>> +++ b/arch/x86/kernel/genapic_64.c
>> @@ -32,10 +32,10 @@
>>   * array during this time.  Is it zeroed when the per_cpu
>>   * data area is removed.
>>   */
>> -u8 x86_cpu_to_apicid_init[NR_CPUS] __initdata
>> +u16 x86_cpu_to_apicid_init[NR_CPUS] __initdata
>>  					= { [0 ... NR_CPUS-1] = BAD_APICID };
>>  void *x86_cpu_to_apicid_ptr;
>> -DEFINE_PER_CPU(u8, x86_cpu_to_apicid) = BAD_APICID;
>> +DEFINE_PER_CPU(u16, x86_cpu_to_apicid) = BAD_APICID;
>>  EXPORT_PER_CPU_SYMBOL(x86_cpu_to_apicid);
>>  
>>  struct genapic __read_mostly *genapic = &apic_flat;
>> --- a/arch/x86/kernel/mpparse_64.c
>> +++ b/arch/x86/kernel/mpparse_64.c
>> @@ -67,7 +67,7 @@ unsigned disabled_cpus __cpuinitdata;
>>  /* Bitmask of physically existing CPUs */
>>  physid_mask_t phys_cpu_present_map = PHYSID_MASK_NONE;
>>  
>> -u8 bios_cpu_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = BAD_APICID };
>> +u16 bios_cpu_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = BAD_APICID };
>>  
>>  
>>  /*
>> @@ -132,7 +132,7 @@ static void __cpuinit MP_processor_info(
>>  	 * area is created.
>>  	 */
>>  	if (x86_cpu_to_apicid_ptr) {
>> -		u8 *x86_cpu_to_apicid = (u8 *)x86_cpu_to_apicid_ptr;
>> +		u16 *x86_cpu_to_apicid = (u16 *)x86_cpu_to_apicid_ptr;
>>  		x86_cpu_to_apicid[cpu] = m->mpc_apicid;
>>  	} else {
>>  		per_cpu(x86_cpu_to_apicid, cpu) = m->mpc_apicid;
>> --- a/arch/x86/kernel/smpboot_64.c
>> +++ b/arch/x86/kernel/smpboot_64.c
>> @@ -65,7 +65,7 @@ int smp_num_siblings = 1;
>>  EXPORT_SYMBOL(smp_num_siblings);
>>  
>>  /* Last level cache ID of each logical CPU */
>> -DEFINE_PER_CPU(u8, cpu_llc_id) = BAD_APICID;
>> +DEFINE_PER_CPU(u16, cpu_llc_id) = BAD_APICID;
>>  
>>  /* Bitmask of currently online CPUs */
>>  cpumask_t cpu_online_map __read_mostly;
>> --- a/arch/x86/mm/numa_64.c
>> +++ b/arch/x86/mm/numa_64.c
>> @@ -627,7 +627,7 @@ void __init init_cpu_to_node(void)
>>  	int i;
>>  
>>  	for (i = 0; i < NR_CPUS; i++) {
>> -		u8 apicid = x86_cpu_to_apicid_init[i];
>> +		u16 apicid = x86_cpu_to_apicid_init[i];
>>  
>>  		if (apicid == BAD_APICID)
>>  			continue;
>> --- a/arch/x86/mm/srat_64.c
>> +++ b/arch/x86/mm/srat_64.c
>> @@ -130,6 +130,9 @@ void __init
>>  acpi_numa_processor_affinity_init(struct acpi_srat_cpu_affinity *pa)
>>  {
>>  	int pxm, node;
>> +	int apic_id;
>> +
>> +	apic_id = pa->apic_id;
>>  	if (srat_disabled())
>>  		return;
>>  	if (pa->header.length != sizeof(struct acpi_srat_cpu_affinity)) {
>> @@ -145,10 +148,10 @@ acpi_numa_processor_affinity_init(struct
>>  		bad_srat();
>>  		return;
>>  	}
>> -	apicid_to_node[pa->apic_id] = node;
>> +	apicid_to_node[apic_id] = node;
>>  	acpi_numa = 1;
>>  	printk(KERN_INFO "SRAT: PXM %u -> APIC %u -> Node %u\n",
>> -	       pxm, pa->apic_id, node);
>> +	       pxm, apic_id, node);
>>  }
>>  
>>  int update_end_of_memory(unsigned long end) {return -1;}
>> @@ -343,7 +346,8 @@ int __init acpi_scan_nodes(unsigned long
>>  	/* First clean up the node list */
>>  	for (i = 0; i < MAX_NUMNODES; i++) {
>>  		cutoff_node(i, start, end);
>> -		if ((nodes[i].end - nodes[i].start) < NODE_MIN_SIZE) {
>> +		/* ZZZ why was this needed. At least add a comment */
>> +		if (nodes[i].end && (nodes[i].end - nodes[i].start) < NODE_MIN_SIZE) {
> 
> Care to actually add a comment? This looks like a note to yourself that
> got missed.
> 
>>  			unparse_node(i);
>>  			node_set_offline(i);
>>  		}
>> @@ -384,6 +388,12 @@ int __init acpi_scan_nodes(unsigned long
>>  }
>>  
>>  #ifdef CONFIG_NUMA_EMU
>> +static int fake_node_to_pxm_map[MAX_NUMNODES] __initdata = {
>> +	[0 ... MAX_NUMNODES-1] = PXM_INVAL
>> +};
>> +static unsigned char fake_apicid_to_node[MAX_LOCAL_APIC] __initdata = {
>> +	[0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE
>> +};
>>  static int __init find_node_by_addr(unsigned long addr)
>>  {
>>  	int ret = NUMA_NO_NODE;
>> @@ -414,12 +424,6 @@ static int __init find_node_by_addr(unsi
>>  void __init acpi_fake_nodes(const struct bootnode *fake_nodes, int num_nodes)
>>  {
>>  	int i, j;
>> -	int fake_node_to_pxm_map[MAX_NUMNODES] = {
>> -		[0 ... MAX_NUMNODES-1] = PXM_INVAL
>> -	};
>> -	unsigned char fake_apicid_to_node[MAX_LOCAL_APIC] = {
>> -		[0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE
>> -	};
>>  
>>  	printk(KERN_INFO "Faking PXM affinity for fake nodes on real "
>>  			 "topology.\n");
>> --- a/include/asm-x86/processor.h
>> +++ b/include/asm-x86/processor.h
>> @@ -86,14 +86,14 @@ struct cpuinfo_x86 {
>>  #ifdef CONFIG_SMP
>>  	cpumask_t llc_shared_map;	/* cpus sharing the last level cache */
>>  #endif
>> -	unsigned char x86_max_cores;	/* cpuid returned max cores value */
>> -	unsigned char apicid;
>> -	unsigned short x86_clflush_size;
>> +	u16 x86_max_cores;		/* cpuid returned max cores value */
>> +	u16 apicid;
>> +	u16 x86_clflush_size;
>>  #ifdef CONFIG_SMP
>> -	unsigned char booted_cores;	/* number of cores as seen by OS */
>> -	__u8 phys_proc_id; 		/* Physical processor id. */
>> -	__u8 cpu_core_id;  		/* Core id */
>> -	__u8 cpu_index;			/* index into per_cpu list */
>> +	u16 booted_cores;		/* number of cores as seen by OS */
>> +	u16 phys_proc_id; 		/* Physical processor id. */
>> +	u16 cpu_core_id;  		/* Core id */
>> +	u16 cpu_index;			/* index into per_cpu list */
>>  #endif
>>  } __attribute__((__aligned__(SMP_CACHE_BYTES)));
>>  
>> --- a/include/asm-x86/smp_64.h
>> +++ b/include/asm-x86/smp_64.h
>> @@ -26,14 +26,14 @@ extern void unlock_ipi_call_lock(void);
>>  extern int smp_call_function_mask(cpumask_t mask, void (*func)(void *),
>>  				  void *info, int wait);
>>  
>> -extern u8 __initdata x86_cpu_to_apicid_init[];
>> +extern u16 __initdata x86_cpu_to_apicid_init[];
>>  extern void *x86_cpu_to_apicid_ptr;
>> -extern u8 bios_cpu_apicid[];
>> +extern u16 bios_cpu_apicid[];
>>  
>>  DECLARE_PER_CPU(cpumask_t, cpu_sibling_map);
>>  DECLARE_PER_CPU(cpumask_t, cpu_core_map);
>> -DECLARE_PER_CPU(u8, cpu_llc_id);
>> -DECLARE_PER_CPU(u8, x86_cpu_to_apicid);
>> +DECLARE_PER_CPU(u16, cpu_llc_id);
>> +DECLARE_PER_CPU(u16, x86_cpu_to_apicid);
>>  
>>  static inline int cpu_present_to_apicid(int mps_cpu)
>>  {
>>
>> -- 
>>
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