Class: Raindrops

Inherits:

Object

• Object
• Raindrops

Defined in:

lib/raindrops.rb,
ext/raindrops/raindrops.c

Overview

Each Raindrops object is a container that holds several counters. It is internally a page-aligned, shared memory area that allows atomic increments, decrements, assignments and reads without any locking.

rd = Raindrops.new 4
rd.incr(0, 1)   -> 1
rd.to_ary       -> [ 1, 0, 0, 0 ]

Unlike many classes in this package, the core Raindrops class is intended to be portable to all reasonably modern *nix systems supporting mmap(). Please let us know if you have portability issues, patches or pull requests at raindrops@librelist.org

Defined Under Namespace

Modules: Aggregate, Linux Classes: InetDiagSocket, LastDataRecv, ListenStats, Middleware, Struct, TCP_Info, Watcher

Constant Summary

PAGE_SIZE =

The size of one page of memory for a mmap()-ed Raindrops region. Typically 4096 bytes under Linux.

SIZET2NUM(rd_page_size)

SIZE =

The size (in bytes) of a slot in a Raindrops object. This is the size of a word on single CPU systems and the size of the L1 cache line size if detectable.

Defaults to 128 bytes if undetectable.

SIZET2NUM(raindrop_size)

MAX =

The maximum value a raindrop counter can hold

ULONG2NUM((unsigned long)-1)

Instance Method Summary

• #[](index) ⇒ Object

  rd -> value.

• #[]=(index, value) ⇒ Object

  rd = value.

• #capa ⇒ Object

  rd.capa -> Integer.

• #decr(*args) ⇒ Object

  rd.decr(index[, number]) -> result.

• #evaporate! ⇒ Object

  rd.evaporate! -> nil.

• #incr(*args) ⇒ Object

  rd.incr(index[, number]) -> result.

• #initialize(size) ⇒ Object constructor

  Raindrops.new(size) -> raindrops object.

• #initialize_copy(source) ⇒ Object

  rd.dup -> rd_copy.

• #size ⇒ Object

  rd.size -> Integer.

• #size=(new_size) ⇒ Object

  rd.size = new_size.

• #to_ary ⇒ Object

  rd.to_ary -> Array.

Constructor Details

#initialize(size) ⇒ Object

Raindrops.new(size) -> raindrops object

Initializes a Raindrops object to hold size counters. size is only a hint and the actual number of counters the object has is dependent on the CPU model, number of cores, and page size of the machine. The actual size of the object will always be equal or greater than the specified size.

# File 'ext/raindrops/raindrops.c', line 86

static VALUE init(VALUE self, VALUE size)
{
	struct raindrops *r = DATA_PTR(self);
	int tries = 1;
	size_t tmp;

	if (r->drops != MAP_FAILED)
		rb_raise(rb_eRuntimeError, "already initialized");

	r->size = NUM2SIZET(size);
	if (r->size < 1)
		rb_raise(rb_eArgError, "size must be >= 1");

	tmp = PAGE_ALIGN(raindrop_size * r->size);
	r->capa = tmp / raindrop_size;
	assert(PAGE_ALIGN(raindrop_size * r->capa) == tmp && "not aligned");

retry:
	r->drops = mmap(NULL, tmp,
	                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");
	}
	r->pid = getpid();

	return self;
}

Instance Method Details

#[](index) ⇒ Object

rd -> value

Returns the value of the slot designated by index

# File 'ext/raindrops/raindrops.c', line 319

static VALUE aref(VALUE self, VALUE index)
{
	return  ULONG2NUM(*addr_of(self, index));
}

#[]=(index, value) ⇒ Object

rd = value

Assigns value to the slot designated by index

# File 'ext/raindrops/raindrops.c', line 304

static VALUE aset(VALUE self, VALUE index, VALUE value)
{
	unsigned long *addr = addr_of(self, index);

	*addr = NUM2ULONG(value);

	return value;
}

#capa ⇒ Object

rd.capa -> Integer

Returns the number of slots allocated (but not necessarily used) by the Raindrops object.

# File 'ext/raindrops/raindrops.c', line 194

static VALUE capa(VALUE self)
{
	return SIZET2NUM(get(self)->capa);
}

#decr(*args) ⇒ Object

rd.decr(index[, number]) -> result

Decrements the value referred to by the index by number. number defaults to 1 if unspecified.

# File 'ext/raindrops/raindrops.c', line 257

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));
}

#evaporate! ⇒ Object

rd.evaporate! -> nil

Releases mmap()-ed memory allocated for the Raindrops object back to the OS. The Ruby garbage collector will also release memory automatically when it is not needed, but this forces release under high memory pressure.

# File 'ext/raindrops/raindrops.c', line 346

static VALUE evaporate_bang(VALUE self)
{
	struct raindrops *r = get(self);
	void *addr = r->drops;

	r->drops = MAP_FAILED;
	if (munmap(addr, raindrop_size * r->capa) != 0)
		rb_sys_fail("munmap");
	return Qnil;
}

#incr(*args) ⇒ Object

rd.incr(index[, number]) -> result

Increments the value referred to by the index by number. number defaults to 1 if unspecified.

# File 'ext/raindrops/raindrops.c', line 243

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));
}

#initialize_copy(source) ⇒ Object

rd.dup -> rd_copy

Duplicates and snapshots the current state of a Raindrops object.

# File 'ext/raindrops/raindrops.c', line 205

static VALUE init_copy(VALUE dest, VALUE source)
{
	struct raindrops *dst = DATA_PTR(dest);
	struct raindrops *src = get(source);

	init(dest, SIZET2NUM(src->size));
	memcpy(dst->drops, src->drops, raindrop_size * src->size);

	return dest;
}

#size ⇒ Object

rd.size -> Integer

Returns the number of counters a Raindrops object can hold. Due to page alignment, this is always equal or greater than the number of requested slots passed to Raindrops.new

# File 'ext/raindrops/raindrops.c', line 293

static VALUE size(VALUE self)
{
	return SIZET2NUM(get(self)->size);
}

#size=(new_size) ⇒ Object

rd.size = new_size

Increases or decreases the current capacity of our Raindrop. Raises RangeError if new_size is too big or small for the current backing store

# File 'ext/raindrops/raindrops.c', line 174

static VALUE setsize(VALUE self, VALUE new_size)
{
	size_t new_rd_size = NUM2SIZET(new_size);
	struct raindrops *r = get(self);

	if (new_rd_size <= r->capa)
		r->size = new_rd_size;
	else
		resize(r, new_rd_size);

	return new_size;
}

#to_ary ⇒ Object

rd.to_ary -> Array

converts the Raindrops structure to an Array

# File 'ext/raindrops/raindrops.c', line 270

static VALUE to_ary(VALUE self)
{
	struct raindrops *r = get(self);
	VALUE rv = rb_ary_new2(r->size);
	size_t i;
	unsigned long base = (unsigned long)r->drops;

	for (i = 0; i < r->size; i++) {
		rb_ary_push(rv, ULONG2NUM(*((unsigned long *)base)));
		base += raindrop_size;
	}

	return rv;
}