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Subject[PATCH v6 2/3] x86/topology: Avoid wasting 128k for package id array
Date
From: Andi Kleen <ak@linux.intel.com>

I was looking at large early boot allocations and noticed that
since (1f12e32f x86/topology: Create logical package id)
every 64bit system allocates a 128k array to convert logical
package ids.

This happens because the array is sized for
MAX_LOCAL_APIC and that is always 32k on 64bit systems,
and it needs 4 bytes for each entry.

This is fairly wasteful, especially for the common case
of having only one socket, where we need 128K just to store
a single 4 byte value.

Store the logical processor id in cpudata. Add a set flag that indicates
that the cpu's cpudata entry has been written.

[v2]: Decrease logical_packages when the last thread in a socket is
removed.
[v3]: Add more logic to keep logical and physical package IDs
in synch.
[v4]: Keep logical mapping static by using hybrid approach of a small
logical
to physical array and keeping logical cpu information in cpu_data.
[v5]: Change kmalloc to GFP_ATOMIC to fix "sleeping function" warning on
virtual machines. Remove phys_pkg_id. Add spinlock to avoid concurrency
issues.
[v6]: Revert back to storing logical processor ID in cpudata, and
add set flag to indicate that boot_cpu_data was written to a cpu's
cpu_data.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Piotr Luc <piotr.luc@intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: He Chen <he.chen@linux.intel.com>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/include/asm/processor.h | 1 +
arch/x86/kernel/smpboot.c | 75 ++++++++++++++++------------------------
2 files changed, 30 insertions(+), 46 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index bdac19ab2488..44fd3512442f 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -132,6 +132,7 @@ struct cpuinfo_x86 {
/* Index into per_cpu list: */
u16 cpu_index;
u32 microcode;
+ unsigned set : 1;
} __randomize_layout;

struct cpuid_regs {
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ad59edd84de7..838d36ff7ba6 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -100,9 +100,6 @@ DEFINE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
EXPORT_PER_CPU_SYMBOL(cpu_info);

/* Logical package management. We might want to allocate that dynamically */
-static int *physical_to_logical_pkg __read_mostly;
-static unsigned long *physical_package_map __read_mostly;;
-static unsigned int max_physical_pkg_id __read_mostly;
unsigned int __max_logical_packages __read_mostly;
EXPORT_SYMBOL(__max_logical_packages);
static unsigned int logical_packages __read_mostly;
@@ -278,6 +275,25 @@ static void notrace start_secondary(void *unused)
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

+/**
+ * topology_phys_to_logical_pkg - Map a physical package id to a logical
+ *
+ * Returns logical package id or -1 if not found
+ */
+int topology_phys_to_logical_pkg(unsigned int phys_pkg)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ if (cpu_data(cpu).phys_proc_id == phys_pkg &&
+ cpu_data(cpu).set) {
+ return cpu_data(cpu).logical_proc_id;
+ }
+ }
+ return -1;
+}
+EXPORT_SYMBOL(topology_phys_to_logical_pkg);
+
/**
* topology_update_package_map - Update the physical to logical package map
* @pkg: The physical package id as retrieved via CPUID
@@ -285,17 +301,11 @@ static void notrace start_secondary(void *unused)
*/
int topology_update_package_map(unsigned int pkg, unsigned int cpu)
{
- unsigned int new;
-
- /* Called from early boot ? */
- if (!physical_package_map)
- return 0;
-
- if (pkg >= max_physical_pkg_id)
- return -EINVAL;
+ int new;

- /* Set the logical package id */
- if (test_and_set_bit(pkg, physical_package_map))
+ /* Already available somewhere? */
+ new = topology_phys_to_logical_pkg(pkg);
+ if (new >= 0)
goto found;

if (logical_packages >= __max_logical_packages) {
@@ -305,34 +315,17 @@ int topology_update_package_map(unsigned int pkg, unsigned int cpu)
}

new = logical_packages++;
- if (new != pkg) {
+ if (new != pkg)
pr_info("CPU %u Converting physical %u to logical package %u\n",
cpu, pkg, new);
- }
- physical_to_logical_pkg[pkg] = new;
-
found:
- cpu_data(cpu).logical_proc_id = physical_to_logical_pkg[pkg];
+ cpu_data(cpu).logical_proc_id = new;
return 0;
}

-/**
- * topology_phys_to_logical_pkg - Map a physical package id to a logical
- *
- * Returns logical package id or -1 if not found
- */
-int topology_phys_to_logical_pkg(unsigned int phys_pkg)
-{
- if (phys_pkg >= max_physical_pkg_id)
- return -1;
- return physical_to_logical_pkg[phys_pkg];
-}
-EXPORT_SYMBOL(topology_phys_to_logical_pkg);
-
static void __init smp_init_package_map(struct cpuinfo_x86 *c, unsigned int cpu)
{
unsigned int ncpus;
- size_t size;

/*
* Today neither Intel nor AMD support heterogenous systems. That
@@ -363,19 +356,6 @@ static void __init smp_init_package_map(struct cpuinfo_x86 *c, unsigned int cpu)
}

__max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
- logical_packages = 0;
-
- /*
- * Possibly larger than what we need as the number of apic ids per
- * package can be smaller than the actual used apic ids.
- */
- max_physical_pkg_id = DIV_ROUND_UP(MAX_LOCAL_APIC, ncpus);
- size = max_physical_pkg_id * sizeof(unsigned int);
- physical_to_logical_pkg = kmalloc(size, GFP_KERNEL);
- memset(physical_to_logical_pkg, 0xff, size);
- size = BITS_TO_LONGS(max_physical_pkg_id) * sizeof(unsigned long);
- physical_package_map = kzalloc(size, GFP_KERNEL);
-
pr_info("Max logical packages: %u\n", __max_logical_packages);

topology_update_package_map(c->phys_proc_id, cpu);
@@ -389,6 +369,7 @@ void __init smp_store_boot_cpu_info(void)
*c = boot_cpu_data;
c->cpu_index = id;
smp_init_package_map(c, id);
+ cpu_data(id).set = 1;
}

/*
@@ -399,13 +380,15 @@ void smp_store_cpu_info(int id)
{
struct cpuinfo_x86 *c = &cpu_data(id);

- *c = boot_cpu_data;
+ if (cpu_data(id).set == 0)
+ *c = boot_cpu_data;
c->cpu_index = id;
/*
* During boot time, CPU0 has this setup already. Save the info when
* bringing up AP or offlined CPU0.
*/
identify_secondary_cpu(c);
+ cpu_data(id).set = 1;
}

static bool
--
2.15.0.rc0.39.g2f0e14e64
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