482018 - JSOP_POP does not set JSRuntime.gcPoke

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, defect)

Description

[Igor Bukanov]

Currently JSOP_POP in the interpreter does not set JSRuntime.gcPoke which prevents scheduling a GC when the allocator hits the malloc limit heuristics. This can trivially lead to OOM errors when allmost all the allocated memory is a garbage like thbe following example for js shell demonstrates:

@watson~> cat ~/s/x1.js
function f()
{
    var s = Array(5<<20).join(".");
    for (var i = 0; i != 500; ++i) {
        s.substring(1);
    }
}

f();
print('OK');
@watson~> ~/build/js32.tm.dbg/js ~/s/x1.js
/home/igor/s/x1.js:5: out of memory

If in the example the line s.substring(1); would be changes into var tmp = s.substring(1); the shell would successfully run the example.

Comment 1

[Brendan Eich [:brendan]]

Could we not eliminate gcPoke and, if the GC can end up running fruitlessly (called too often with a totally-live heap and no garbage to collect) deal with that problem some other way?

My recollection of gcPoke goes back 13 years. It was a quick and dirty idea for avoiding excessive, fruitless GC runs, but there must be a better way.

/be

Comment 2

[Luke Wagner [:luke]]

This completes w/o OOM.