Instead of using the high water mark for determining this metric, we use
a bitset for all active/used system pages on a V8 heap page. Each time
when allocating a LAB on a page, we add the pages of that memory range
to that bitset. During sweeping we rebuild that bitset from scratch and
replace it with the old one in case free pages are discarded by the GC.
We DCHECK here that the sweeper only ever removes pages. This has the
nice benefit of ensuring that we don't miss any allocations (like we
do now for concurrent allocations).
CommittedPhysicalMemory for a page is then calculated by counting the
set bits in the bitset and multiplying it with the system page size.
This should be simpler to verify and track the "real" effective size
more precisely.
One case where we are partially less precise than the current
implementation is for LABs. In order to reduce complexity we now treat
all pages of a LAB allocation as active immediately. In the current
implementation we tried to only account the actual used part of the LAB
when changing the LAB later. This is more complex to track correctly
but also doesn't account the currently used LAB in effective size.
Change-Id: Ia83df9ad5fbb852f0717c4c396b5074604bd21e9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497363
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79428}
This is a reland of f25cb50a2f
Removed the problematic tests.
The problem with the test was that we try to pop from an empty segment.
GCC flags that as accessing beyond the array (i.e. index is uint16_t
equivalent of -1). Preceding the actual pop is a DCHECK that asserts
the segment isn't empty. In practice, since we have the DCHECK and
access to the segment is always via a Local, this shouldn't be a
problem.
Unfortunately, GCC flags the access regardless. The DCHECK goes through
a function pointer so GCC cannot determine that in our unittest the
DCHECK would crash if index is 0 and the access would not happen (The
indirection was added to allow for test DCHECK handlers that don't
crash, so we can't mark the function pointer as noreturn).
Drive-by: Segment::Pop and Segment::Push rely on the their Local
counterparts checking of emptiness/fullness, so we should always
access segments via Locals. Making the Segment ctor private.
Original change's description:
> Reland "cppgc, heap: Don't eagerly allocate worklist segments"
>
> This is a reland of c99147c65e
>
> Original change's description:
> > cppgc, heap: Don't eagerly allocate worklist segments
> >
> > Bug: chromium:1056170
> > Change-Id: I75a6b5f52bfe8dd71abc086e5d1e060759ad7fc0
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2391254
> > Commit-Queue: Omer Katz <omerkatz@chromium.org>
> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#69778}
>
> Bug: chromium:1056170
> Change-Id: I4633da065976a6b2710d2f23b946fd2af0e65c83
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2401425
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#69806}
Bug: chromium:1056170
Change-Id: I7a122d1a2d20cd4e7c824d249975b4d3df30e03e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2403251
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69829}
