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Let VM control when or if to read env var options (#955)
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Allow Options to be created with MMTK's built-in defaults without
reading options from environment variables, and let the VM decide when
to read options from environment variables.

This will allow VMs to provide default options, override MMTK's default
options, but can be overridden by environment variables. It will also
allow VMs to completely disable the "MMTK_*" variables.

For compatibility reasons, this PR does not change the default behavior
of MMTKBuilder. MMTKBuilder::new will still read from environment
variables, but the new constructor MMTKBuilder::new_no_env_vars will
skip environment variables.

Fixes: #636
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@wks
wks authored Sep 15, 2023
1 parent 14a26b1 commit 42f109b
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Showing 2 changed files with 70 additions and 22 deletions.
11 changes: 10 additions & 1 deletion src/mmtk.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,17 @@ pub struct MMTKBuilder {
}

impl MMTKBuilder {
/// Create an MMTK builder with default options
/// Create an MMTK builder with options read from environment variables, or using built-in
/// default if not overridden by environment variables.
pub fn new() -> Self {
let mut builder = Self::new_no_env_vars();
builder.options.read_env_var_settings();
builder
}

/// Create an MMTK builder with build-in default options, but without reading options from
/// environment variables.
pub fn new_no_env_vars() -> Self {
MMTKBuilder {
options: Options::default(),
}
Expand Down
81 changes: 60 additions & 21 deletions src/util/options.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -235,27 +235,37 @@ macro_rules! options {
_ => panic!("Invalid Options key: {}", s)
}
}
}
impl Default for Options {
fn default() -> Self {
let mut options = Options {
$($name: MMTKOption::new($default, $validator, $env_var,$command_line)),*
};

// If we have env vars that start with MMTK_ and match any option (such as MMTK_STRESS_FACTOR),
// we set the option to its value (if it is a valid value). Otherwise, use the default value.
/// Create an `Options` instance with built-in default settings.
fn new() -> Self {
Options {
$($name: MMTKOption::new($default, $validator, $env_var, $command_line)),*
}
}

/// Read options from environment variables, and apply those settings to self.
///
/// If we have environment variables that start with `MMTK_` and match any option (such
/// as `MMTK_STRESS_FACTOR`), we set the option to its value (if it is a valid value).
pub fn read_env_var_settings(&mut self) {
const PREFIX: &str = "MMTK_";
for (key, val) in std::env::vars() {
// strip the prefix, and get the lower case string
if let Some(rest_of_key) = key.strip_prefix(PREFIX) {
let lowercase: &str = &rest_of_key.to_lowercase();
match lowercase {
$(stringify!($name) => { options.set_from_env_var(lowercase, &val); },)*
$(stringify!($name) => { self.set_from_env_var(lowercase, &val); },)*
_ => {}
}
}
}
return options;
}
}

impl Default for Options {
/// By default, `Options` instance is created with built-in default settings.
fn default() -> Self {
Self::new()
}
}
]
Expand Down Expand Up @@ -747,7 +757,8 @@ mod tests {
#[test]
fn no_env_var() {
serial_test(|| {
let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.stress_factor, DEFAULT_STRESS_FACTOR);
})
}
Expand All @@ -759,7 +770,8 @@ mod tests {
|| {
std::env::set_var("MMTK_STRESS_FACTOR", "4096");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.stress_factor, 4096);
},
|| {
Expand All @@ -777,7 +789,8 @@ mod tests {
std::env::set_var("MMTK_STRESS_FACTOR", "4096");
std::env::set_var("MMTK_NO_FINALIZER", "true");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.stress_factor, 4096);
assert!(*options.no_finalizer);
},
Expand All @@ -797,7 +810,8 @@ mod tests {
// invalid value, we cannot parse the value, so use the default value
std::env::set_var("MMTK_STRESS_FACTOR", "abc");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.stress_factor, DEFAULT_STRESS_FACTOR);
},
|| {
Expand All @@ -815,7 +829,8 @@ mod tests {
// invalid value, we cannot parse the value, so use the default value
std::env::set_var("MMTK_ABC", "42");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.stress_factor, DEFAULT_STRESS_FACTOR);
},
|| {
Expand All @@ -825,6 +840,24 @@ mod tests {
})
}

#[test]
fn ignore_env_var() {
serial_test(|| {
with_cleanup(
|| {
std::env::set_var("MMTK_STRESS_FACTOR", "42");

let options = Options::default();
// Not calling read_env_var_settings here.
assert_eq!(*options.stress_factor, DEFAULT_STRESS_FACTOR);
},
|| {
std::env::remove_var("MMTK_STRESS_FACTOR");
},
)
})
}

#[test]
fn test_str_option_default() {
serial_test(|| {
Expand All @@ -844,7 +877,8 @@ mod tests {
|| {
std::env::set_var("MMTK_WORK_PERF_EVENTS", "PERF_COUNT_HW_CPU_CYCLES,0,-1");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(
*options.work_perf_events,
PerfEventOptions {
Expand All @@ -868,7 +902,8 @@ mod tests {
// The option needs to start with "hello", otherwise it is invalid.
std::env::set_var("MMTK_WORK_PERF_EVENTS", "PERF_COUNT_HW_CPU_CYCLES");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
// invalid value from env var, use default.
assert_eq!(
*options.work_perf_events,
Expand All @@ -891,7 +926,8 @@ mod tests {
// We did not enable the perf_counter feature. The option will be invalid anyway, and will be set to empty.
std::env::set_var("MMTK_PHASE_PERF_EVENTS", "PERF_COUNT_HW_CPU_CYCLES,0,-1");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
// invalid value from env var, use default.
assert_eq!(
*options.work_perf_events,
Expand All @@ -912,7 +948,8 @@ mod tests {
|| {
std::env::set_var("MMTK_THREAD_AFFINITY", "0-");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
// invalid value from env var, use default.
assert_eq!(*options.thread_affinity, AffinityKind::OsDefault);
},
Expand All @@ -931,7 +968,8 @@ mod tests {
|| {
std::env::set_var("MMTK_THREAD_AFFINITY", "0");

let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(
*options.thread_affinity,
AffinityKind::RoundRobin(vec![0_u16])
Expand Down Expand Up @@ -961,7 +999,8 @@ mod tests {
}

std::env::set_var("MMTK_THREAD_AFFINITY", cpu_list);
let options = Options::default();
let mut options = Options::default();
options.read_env_var_settings();
assert_eq!(*options.thread_affinity, AffinityKind::RoundRobin(vec));
},
|| {
Expand Down

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