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Added cache line size info in SDL_cpuinfo.h
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I also added an implementation to dynamically query it, but didn't expose it since most x86 CPUs have an L1 cache line size of 64 bytes.
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@slouken
slouken committed Jan 28, 2011
1 parent 2273c0b commit 34692e4
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Showing 4 changed files with 121 additions and 67 deletions.
5 changes: 5 additions & 0 deletions include/SDL_cpuinfo.h
View file
Expand Up @@ -39,6 +39,11 @@ extern "C" {
/* *INDENT-ON* */
#endif

/* This is a guess for the cacheline size used for padding, and is correct
* for most x86 processors at this point.
*/
#define SDL_CACHELINE_SIZE 64

/**
* This function returns the number of CPU cores available.
*/
Expand Down
160 changes: 107 additions & 53 deletions src/cpuinfo/SDL_cpuinfo.c
View file
Expand Up @@ -337,73 +337,125 @@ SDL_GetCPUCount()
static const char *
SDL_GetCPUType()
{
static char SDL_CPUType[48];
static char SDL_CPUType[13];

if (!SDL_CPUType[0]) {
int i = 0;
int a, b, c, d;

if (CPU_haveCPUID()) {
cpuid(0x00000000, a, b, c, d);
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
}
if (!SDL_CPUType[0]) {
SDL_strlcpy(SDL_CPUType, "Unknown", sizeof(SDL_CPUType));
}
}
return SDL_CPUType;
}

static const char *
SDL_GetCPUName()
{
static char SDL_CPUName[48];

if (!SDL_CPUName[0]) {
int i = 0;
int a, b, c, d;

if (CPU_haveCPUID()) {
cpuid(0x80000000, a, b, c, d);
if (a >= 0x80000004) {
cpuid(0x80000002, a, b, c, d);
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
cpuid(0x80000003, a, b, c, d);
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
cpuid(0x80000004, a, b, c, d);
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUType[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(a & 0xff); a >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(b & 0xff); b >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(c & 0xff); c >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
SDL_CPUName[i++] = (char)(d & 0xff); d >>= 8;
}
}
if (!SDL_CPUType[0]) {
SDL_strlcpy(SDL_CPUType, "Unknown", sizeof(SDL_CPUType));
if (!SDL_CPUName[0]) {
SDL_strlcpy(SDL_CPUName, "Unknown", sizeof(SDL_CPUName));
}
}
return SDL_CPUType;
return SDL_CPUName;
}

static int
SDL_GetCPUCacheLineSize()
{
const char *cpuType = SDL_GetCPUType();

if (SDL_strcmp(cpuType, "GenuineIntel") == 0) {
int a, b, c, d;

cpuid(0x00000001, a, b, c, d);
return (((b >> 8) & 0xff) * 8);
} else if (SDL_strcmp(cpuType, "AuthenticAMD") == 0) {
int a, b, c, d;

cpuid(0x80000005, a, b, c, d);
return (c & 0xff);
} else {
/* Just make a guess here... */
return SDL_CACHELINE_SIZE;
}
}

static Uint32 SDL_CPUFeatures = 0xFFFFFFFF;
Expand Down Expand Up @@ -521,7 +573,9 @@ int
main()
{
printf("CPU count: %d\n", SDL_GetCPUCount());
printf("CPU name: %s\n", SDL_GetCPUType());
printf("CPU type: %s\n", SDL_GetCPUType());
printf("CPU name: %s\n", SDL_GetCPUName());
printf("CacheLine size: %d\n", SDL_GetCPUCacheLineSize());
printf("RDTSC: %d\n", SDL_HasRDTSC());
printf("MMX: %d\n", SDL_HasMMX());
printf("MMXExt: %d\n", SDL_HasMMXExt());
Expand Down
6 changes: 2 additions & 4 deletions src/timer/SDL_timer.c
View file
Expand Up @@ -24,6 +24,7 @@
#include "SDL_timer.h"
#include "SDL_timer_c.h"
#include "SDL_atomic.h"
#include "SDL_cpuinfo.h"
#include "SDL_thread.h"

/* #define DEBUG_TIMERS */
Expand All @@ -46,9 +47,6 @@ typedef struct _SDL_TimerMap
struct _SDL_TimerMap *next;
} SDL_TimerMap;

/* A reasonable guess */
#define CACHELINE_SIZE 128

/* The timers are kept in a sorted list */
typedef struct {
/* Data used by the main thread */
Expand All @@ -58,7 +56,7 @@ typedef struct {
SDL_mutex *timermap_lock;

/* Padding to separate cache lines between threads */
char pad[CACHELINE_SIZE];
char cache_pad[SDL_CACHELINE_SIZE];

/* Data used to communicate with the timer thread */
SDL_SpinLock lock;
Expand Down
17 changes: 7 additions & 10 deletions test/testatomic.c
View file
Expand Up @@ -243,9 +243,6 @@ void RunEpicTest()
#define NUM_WRITERS 4
#define EVENTS_PER_WRITER 1000000

/* A decent guess for the size of a cache line on this architecture */
#define CACHELINE 64

/* The number of entries must be a power of 2 */
#define MAX_ENTRIES 256
#define WRAP_MASK (MAX_ENTRIES-1)
Expand All @@ -260,22 +257,22 @@ typedef struct
{
SDL_EventQueueEntry entries[MAX_ENTRIES];

char cache_pad1[CACHELINE-((sizeof(SDL_EventQueueEntry)*MAX_ENTRIES)%CACHELINE)];
char cache_pad1[SDL_CACHELINE_SIZE-((sizeof(SDL_EventQueueEntry)*MAX_ENTRIES)%SDL_CACHELINE_SIZE)];

SDL_atomic_t enqueue_pos;

char cache_pad2[CACHELINE-sizeof(SDL_atomic_t)];
char cache_pad2[SDL_CACHELINE_SIZE-sizeof(SDL_atomic_t)];

SDL_atomic_t dequeue_pos;

char cache_pad3[CACHELINE-sizeof(SDL_atomic_t)];
char cache_pad3[SDL_CACHELINE_SIZE-sizeof(SDL_atomic_t)];

#ifdef TEST_SPINLOCK_FIFO
SDL_SpinLock lock;
SDL_atomic_t rwcount;
SDL_atomic_t watcher;

char cache_pad4[CACHELINE-sizeof(SDL_SpinLock)-2*sizeof(SDL_atomic_t)];
char cache_pad4[SDL_CACHELINE_SIZE-sizeof(SDL_SpinLock)-2*sizeof(SDL_atomic_t)];
#endif

volatile SDL_bool active;
Expand Down Expand Up @@ -470,10 +467,10 @@ typedef struct
{
SDL_EventQueue *queue;
int index;
char padding1[CACHELINE-(sizeof(SDL_EventQueue*)+sizeof(int))%CACHELINE];
char padding1[SDL_CACHELINE_SIZE-(sizeof(SDL_EventQueue*)+sizeof(int))%SDL_CACHELINE_SIZE];
int waits;
SDL_bool lock_free;
char padding2[CACHELINE-sizeof(int)-sizeof(SDL_bool)];
char padding2[SDL_CACHELINE_SIZE-sizeof(int)-sizeof(SDL_bool)];
} WriterData;

typedef struct
Expand All @@ -482,7 +479,7 @@ typedef struct
int counters[NUM_WRITERS];
int waits;
SDL_bool lock_free;
char padding[CACHELINE-(sizeof(SDL_EventQueue*)+sizeof(int)*NUM_WRITERS+sizeof(int)+sizeof(SDL_bool))%CACHELINE];
char padding[SDL_CACHELINE_SIZE-(sizeof(SDL_EventQueue*)+sizeof(int)*NUM_WRITERS+sizeof(int)+sizeof(SDL_bool))%SDL_CACHELINE_SIZE];
} ReaderData;

static int FIFO_Writer(void* _data)
Expand Down

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