Make AdjustAmountOfExternalAllocatedMemory() more robust.

Make AdjustAmountOfExternalAllocatedMemory() more robust.

Do not crash if called from a thread without V8 isolate, reset the external
memory counters in case of overflow, bump the external allocation limit.

This will allow us to track typed array allocation and deallocation in WebKit.

BUG=v8:2022, 122097, 42342
R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=12262

[ulan, 2012-08-06 13:01:58]

PTAL

https://chromiumcodereview.appspot.com/10837122/diff/1/src/heap.cc
File src/heap.cc (right):

https://chromiumcodereview.appspot.com/10837122/diff/1/src/heap.cc#newcode5796
src/heap.cc:5796: external_allocation_limit_ = 16 * max_semispace_size_;
The current limit is 80MB for desktop and 40MB for android, which seems a bit
small, so I am bumping it.

[Jakob Kummerow, 2012-08-06 13:13:34]

lgtm

[Erik Corry, 2012-08-07 07:32:13]

https://chromiumcodereview.appspot.com/10837122/diff/1/src/api.cc
File src/api.cc (right):

https://chromiumcodereview.appspot.com/10837122/diff/1/src/api.cc#newcode5279
src/api.cc:5279: if (isolate == NULL || !isolate->IsInitialized() ||
This seems a bit fragile.  If we are silently ignoring some updates then the
external memory count will become incorrect.  This will manifest itself as very
poor performance caused by too frequent GCs.  Perhaps it is better to let it
crash and fix whatever it is that is calling from the wrong thread?

[ulan, 2012-08-07 09:05:52]

https://chromiumcodereview.appspot.com/10837122/diff/1/src/api.cc
File src/api.cc (right):

https://chromiumcodereview.appspot.com/10837122/diff/1/src/api.cc#newcode5279
src/api.cc:5279: if (isolate == NULL || !isolate->IsInitialized() ||
On 2012/08/07 07:32:13, Erik Corry wrote:
> This seems a bit fragile.  If we are silently ignoring some updates then the
> external memory count will become incorrect.  This will manifest itself as
very
> poor performance caused by too frequent GCs.  Perhaps it is better to let it
> crash and fix whatever it is that is calling from the wrong thread?

It's tricky with all those transfers between threads. We want this function to
be a no-op if called from the wrong thread, otherwise we would have to add guard
in each thread:
if (is_v8_initialized()) AdjustAmountOfExternalAllocatedMemory();

At the moment GC is triggered based on the delta of externally allocated  memory
since the last GC (the absolute value of externally allocated memory doesn't
matter). So even if we occasionally miss some updates, this error won't spread
beyond one GC. Of course if we change our heuristics to depend on absolute value
of external memory then we will have a problem.