pretenuring.js - mozsearch

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// Test nursery string allocation and pretenuring.

gczeal(0);

gcparam("semispaceNurseryEnabled", 0);

gcparam("minNurseryBytes", 4096 * 1024);

gcparam("maxNurseryBytes", 4096 * 1024);

gc();

// String allocation in the nursery is initially enabled.

assertEq(nurseryStringsEnabled(), true);

// Literal strings are atoms (which are always tenured).

assertEq(isNurseryAllocated("foo"), false);

// The result of Number.toString is nursery allocated.

assertEq(isNurseryAllocated((1234).toString()), true);

// Ropes are nursery allocated.

let s = "bar";

assertEq(isNurseryAllocated("foo" + s), true);

// Dependent strings are nursery allocated.

assertEq(isNurseryAllocated("foobar".substr(1)), true);

// The testing function 'newString' allows control over which heap is used.

assertEq(isNurseryAllocated(newString("foobar", { tenured: true })), false);

assertEq(isNurseryAllocated(newString("foobar", { tenured: false })), true);

// Allocating lots of strings which survive nursery collection disables

// allocating strings in the nursery.

let a = [];

for (let i = 1; i < 500000; i++) {

  a.push(i.toString());

gc();

assertEq(nurseryStringsEnabled(), false);

a = undefined;

// When a large number of tenured strings die very soon after allocation,

// pretenuring for that zone is reset and nursery allocation enabled again.

gc();

assertEq(nurseryStringsEnabled(), false);

let initGCNumber = gcparam('majorGCNumber');

while (!nurseryStringsEnabled() && gcparam('majorGCNumber') < initGCNumber + 3) {

  for (let i = 1; i < 100000; i++) {

    a = i.toString();

assertEq(nurseryStringsEnabled(), true);