I collected statistics for the sizes and capacities of growable arrays which are promoted to old-space or survive an old-space gc when running dart2js and Fasta. For these applications, the vast majority of arrays stay empty. More than half of the total object size of promoted backing arrays is backing for empty growable arrays.
Furthermore, since the overhead for an array is 3 words (header, type parameters and length), and object sizes are rounded up to an even number of words, we waste one word for all even-sized arrays.
This CL changes the growth strategy so that empty growable arrays are created with a shared, zero-sized array as backing, avoiding the allocation of a backing array if no elements are added. When the array needs to grow, it starts out at 3 and grows to double size plus one each time: 7, 15, 31, ...
A few places in the VM code need to handle these shared, zero-sized arrays specially. In particular, the Array::MakeArray function needs to allocate a new, empty array if its result is to be returned to Dart code.
Benchmarks suggest that the change improves memory usage by a few percent overall and does not significantly affect run time.
BUG=
R=erikcorry@google.com
Review-Url: https://codereview.chromium.org/2949803002 .
- Don't tick vm tags for background threads so the Observatory's summary pie chart reflects how the mutator spent its time.
- Similarly, don't factor background samples in the CPU profile view.
- Do include background samples in the timeline view.
Use a different event name for background compilations.
Add timeline events for the mark and sweep tasks.
Reload the isolate list when refreshing the timeline view so it includes profile ticks when the page is loading directly (e.g., F5) instead of only after visiting the vm page.
Fix loading the timeline when profiling is disabled.
BUG=
R=johnmccutchan@google.com
Review URL: https://codereview.chromium.org/1814813003 .
- uses thread execution status transition to track when a thread is in a safepoint or needs to block for a safepoint
- introduces a monitor per Thread object
- uses a per thread safepoint handshake between the thread requesting a safepoint and the requested thread.
The ThreadRegistry class now contains only the thread list for an isolate and the functionality of scheduling a thread onto an Isolate and unscheduling it from teh isolate. We could fold this functionality into the Isolate class in a different CL.
R=rmacnak@google.com, zra@google.com
Review URL: https://codereview.chromium.org/1541073002 .
- Ensure that no new OSThreads are created once the VM is in shutdown mode
- Do not query thread_list_head_ without a lock (this leads to the race which causes two threads to delete the lock and TLS at the same time)
BUG=25236
R=zra@google.com
Review URL: https://codereview.chromium.org/1537543002 .
In release mode, there seems to be nothing to prevent this.
In debug mode, the "Verify" call waits for the sweeper, but there is still a race between the task count update and the ExitIsolateAsHelper call, which could cause problems.
Fix both of these, and add more assertions and verbose error messages.
- make sweeper task cleanly exit isolate *before* notifying
- wait for sweeper before shutting down isolate
- verbose pthread failures
BUG=
R=asiva@google.com
Review URL: https://codereview.chromium.org//1233563004 .
* Use real isolate in concurrent sweeper rather than shallow copy.
The only part of the isolate, other than the page being swept, used by the sweeper is the class table (via RawObject::Size), which is now safe to read concurrently (copy-on-write).
* Do not eagerly destroy a VM thread whenever it exits an isolate.
This extends the lifetime of a VM thread across entering/exiting multiple isolates. This is necessary in case an embedder callback executes during
compilation and switches/spawns isolates.
For embedder threads, since there is no API to signal "I'm done using the VM in this thread", this means we leak the (small) Thread structure.
For our own ThreadPool threads, we explicitly clean up.
BUG=23153
R=iposva@google.com
Review URL: https://codereview.chromium.org//1136143003
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@45810 260f80e4-7a28-3924-810f-c04153c831b5
Ryan Macnak