Remove GC in harness_begin. full_heap_system_gc defaults to true #1141
Conversation
|
@wks Feel free to make code changes in the PR. |
| * The user applications and benchmarks are responsible to trigger a GC before calling `harness_begin`. | ||
| * `handle_user_collection_request` | ||
| * The runtime option `full_heap_sytem_gc` defaults to `true` now (it used to be `false` by default). | ||
| The GC triggered by this function will be a full heap GC by default. |
There was a problem hiding this comment.
You can add link to this PR in a "See also:" section.
| @@ -75,6 +75,23 @@ See also: | |||
| - PR: <https://github.com/mmtk/mmtk-core/pull/1134> | |||
| - Example: <https://github.com/mmtk/mmtk-openjdk/pull/274> | |||
|
|
|||
| ### Remove GC in `harness_begin` | |||
There was a problem hiding this comment.
Because the versions are in the reversed order, we should list changes in the reversed order, too.
src/mmtk.rs
Outdated
| force: bool, | ||
| exhaustive: bool, | ||
| ) { | ||
| pub fn handle_user_collection_request(&self, tls: VMMutatorThread) { |
There was a problem hiding this comment.
Some VMs gives the user fine-grained control of whether to trigger a full-heap GC or a minor GC. In CRuby, the GC::start method uses the full_mark parameter for that. The current master branch of mmtk-ruby ignores this because it still doesn't support StickyImmix, but will enable StickyImmix once we fix the side forwarding bits bug. We should leave a public API for the VM to choose whether to perform an exhaustive GC.
Note: memory_manager::handle_user_collection_request is public, and MMTK::handle_user_collection_request is a public method, too.
The OpenJDK binding calls memory_manager::handle_user_collection_request which does not have the force and exhaustive parameters. I suggest we leave Option::full_heap_system_gc and MMTK::handle_user_collection_request unchanged, but change memory_manager::handle_user_collection_request to pass true and true to MMTK::handle_user_collection_request.
There was a problem hiding this comment.
change memory_manager::handle_user_collection_request to pass true and true to MMTK::handle_user_collection_request
In this case, MMTk basically ignores those two options: ignore_system_gc is ignored, as we always force GC, and full_heap_system_gc is also ignored as we always do full heap/exhaustive GC.
There was a problem hiding this comment.
No. MMTK::handle_user_collection_request is public, too. The Ruby VM, for example, can directly call mmtk.handle_user_collection_request(tls, false, true) to trigger full-heap GC, and call mmtk.handle_user_collection_request(tls, false, false) to trigger nursery GC. OpenJDK can call memory_manager::handle_user_collection_request(tls) to use the default force and exhaustive arguments.
There was a problem hiding this comment.
Well, I think a more elegant solution is to change the argument of MMTK::handle_user_collection_request to take one single UserCollectionArgs value:
struct UserCollectionArgs {
force: bool,
exhaustive: bool,
}
impl default for UserCollectionArgs {
fn default() -> Self {
Self { force: true, exhaustive: true }
}
}This will allow the VM binding to always call mmtk.handle_user_collection_request(tls, UserCollectionArgs::default()) if they want the default value, or call mmtk.handle_user_collection_request(tls, UserCollectionArgs { exhaustive: true, ..Default::default() } if they want to customise. But that'll be an API-breaking change.
ful_heap_system_gc from options.
|
As we discussed earlier, I remove the option @wks Can you take a look at this PR? If the changes look fine, I will fix the bindings for the breaking change. |
| /// This is usually called by the benchmark harness as its last step before the actual benchmark. | ||
| pub fn harness_begin(&self, tls: VMMutatorThread) { | ||
| pub fn harness_begin(&self, _tls: VMMutatorThread) { |
There was a problem hiding this comment.
Since we decided that this is going to be an API-breaking change, we can remove this unused _tls argument.
| pub fn harness_begin(&self, _tls: VMMutatorThread) { | |
| pub fn harness_begin(&self) { |
| @@ -403,35 +401,26 @@ impl<VM: VMBinding> MMTK<VM> { | |||
| } | |||
|
|
|||
| /// The application code has requested a collection. This is just a GC hint, and | |||
| /// we may ignore it. | |||
| /// we may ignore it (See `ignore_system_gc` and `full_heap_system_gc` in [`crate::util::options::Options`]). | |||
There was a problem hiding this comment.
We removed full_heap_system_gc.
| /// we may ignore it (See `ignore_system_gc` and `full_heap_system_gc` in [`crate::util::options::Options`]). | |
| /// we may ignore it (See `ignore_system_gc` in [`crate::util::options::Options`]). |
This PR fixes #1140.