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| | #include <ruby.h>
#include <sys/mman.h>
#include <assert.h>
#include <errno.h>
#include <stddef.h>
/*
* most modern CPUs have a cache-line size of 64 or 128.
* We choose a bigger one by default since our structure is not
* heavily used
*/
#ifndef CACHE_LINE_SIZE
# define CACHE_LINE_SIZE 128
#endif
/* each raindrop is a counter */
struct raindrop {
union {
unsigned long counter;
unsigned char padding[CACHE_LINE_SIZE];
} as;
} __attribute__((packed));
/* allow mmap-ed regions can store more than one raindrop */
struct raindrops {
long size;
struct raindrop *drops;
};
/* called by GC */
static void evaporate(void *ptr)
{
struct raindrops *r = ptr;
if (r->drops) {
int rv = munmap(r->drops, sizeof(struct raindrop) * r->size);
if (rv != 0)
rb_bug("munmap failed in gc: %s", strerror(errno));
}
xfree(ptr);
}
/* automatically called at creation (before initialize) */
static VALUE alloc(VALUE klass)
{
struct raindrops *r;
return Data_Make_Struct(klass, struct raindrops, NULL, evaporate, r);
}
static struct raindrops *get(VALUE self)
{
struct raindrops *r;
Data_Get_Struct(self, struct raindrops, r);
return r;
}
/* initializes a Raindrops object to hold +size+ elements */
static VALUE init(VALUE self, VALUE size)
{
struct raindrops *r = get(self);
int tries = 1;
if (r->drops)
rb_raise(rb_eRuntimeError, "already initialized");
r->size = NUM2LONG(size);
if (r->size < 1)
rb_raise(rb_eArgError, "size must be >= 1");
retry:
r->drops = mmap(NULL, sizeof(struct raindrop) * r->size,
PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
if (r->drops == MAP_FAILED) {
if ((errno == EAGAIN || errno == ENOMEM) && tries-- > 0) {
rb_gc();
goto retry;
}
rb_sys_fail("mmap");
}
return self;
}
/* :nodoc */
static VALUE init_copy(VALUE dest, VALUE source)
{
struct raindrops *dst = get(dest);
struct raindrops *src = get(source);
init(dest, LONG2NUM(src->size));
memcpy(dst->drops, src->drops, sizeof(struct raindrop) * src->size);
return dest;
}
static unsigned long *addr_of(VALUE self, VALUE index)
{
struct raindrops *r = get(self);
unsigned long off = FIX2ULONG(index) * sizeof(struct raindrop);
if (off >= sizeof(struct raindrop) * r->size)
rb_raise(rb_eArgError, "offset overrun");
return (unsigned long *)((unsigned long)r->drops + off);
}
static unsigned long incr_decr_arg(int argc, const VALUE *argv)
{
if (argc > 2 || argc < 1)
rb_raise(rb_eArgError,
"wrong number of arguments (%d for 1+)", argc);
return argc == 2 ? NUM2ULONG(argv[1]) : 1;
}
/* increments the value referred to by the +index+ constant by 1 */
static VALUE incr(int argc, VALUE *argv, VALUE self)
{
unsigned long nr = incr_decr_arg(argc, argv);
return ULONG2NUM(__sync_add_and_fetch(addr_of(self, argv[0]), nr));
}
/* decrements the value referred to by the +index+ constant by 1 */
static VALUE decr(int argc, VALUE *argv, VALUE self)
{
unsigned long nr = incr_decr_arg(argc, argv);
return ULONG2NUM(__sync_sub_and_fetch(addr_of(self, argv[0]), nr));
}
/* converts the raindrops structure to an Array */
static VALUE to_ary(VALUE self)
{
struct raindrops *r = get(self);
VALUE rv = rb_ary_new2(r->size);
long i;
unsigned long base = (unsigned long)r->drops;
for (i = 0; i < r->size; i++) {
rb_ary_push(rv, ULONG2NUM(*((unsigned long *)base)));
base += sizeof(struct raindrop);
}
return rv;
}
static VALUE size(VALUE self)
{
return LONG2NUM(get(self)->size);
}
static VALUE aset(VALUE self, VALUE index, VALUE value)
{
unsigned long *addr = addr_of(self, index);
*addr = NUM2ULONG(value);
return value;
}
static VALUE aref(VALUE self, VALUE index)
{
return ULONG2NUM(*addr_of(self, index));
}
#ifdef __linux__
void Init_raindrops_linux_inet_diag(void);
#endif
void Init_raindrops_ext(void)
{
VALUE cRaindrops = rb_define_class("Raindrops", rb_cObject);
rb_define_alloc_func(cRaindrops, alloc);
rb_define_method(cRaindrops, "initialize", init, 1);
rb_define_method(cRaindrops, "incr", incr, -1);
rb_define_method(cRaindrops, "decr", decr, -1);
rb_define_method(cRaindrops, "to_ary", to_ary, 0);
rb_define_method(cRaindrops, "[]", aref, 1);
rb_define_method(cRaindrops, "[]=", aset, 2);
rb_define_method(cRaindrops, "size", size, 0);
rb_define_method(cRaindrops, "initialize_copy", init_copy, 1);
#ifdef __linux__
Init_raindrops_linux_inet_diag();
#endif
}
|