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libstore: replace Goal::WaitForSlot with semaphores

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now that we have an event loop in the worker we can use it and its
magical execution suspending properties to replace the slot counts
we managed explicitly with semaphores and raii tokens. technically
this would not have needed an event loop base to be doable, but it
is a whole lot easier to wait for a token to be available if there
is a callback mechanism ready for use that doesn't require a whole
damn dedicated abstract method in Goal to work, and specific calls
to that dedicated method strewn all over the worker implementation

Change-Id: I1da7cf386d94e2bbf2dba9b53ff51dbce6a0cff7
This commit is contained in:
eldritch horrors 2024-09-24 00:21:16 +02:00
parent bf32085d63
commit 852da07b67
10 changed files with 58 additions and 124 deletions
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7
src/libstore/build/derivation-goal.cc
View file

@ -134,9 +134,9 @@ Goal::Finished DerivationGoal::timedOut(Error && ex)
}
kj::Promise<Result<Goal::WorkResult>> DerivationGoal::work(bool inBuildSlot) noexcept
kj::Promise<Result<Goal::WorkResult>> DerivationGoal::work() noexcept
{
return (this->*state)(inBuildSlot);
return (this->*state)(slotToken.valid());
}
void DerivationGoal::addWantedOutputs(const OutputsSpec & outputs)
@ -783,7 +783,7 @@ try {
buildResult.startTime = time(0); // inexact
state = &DerivationGoal::buildDone;
started();
return {{WaitForWorld{std::move(a.promise), false}}};
return {{WaitForWorld{std::move(a.promise)}}};
},
[&](HookReply::Postpone) -> std::optional<kj::Promise<Result<WorkResult>>> {
/* Not now; wait until at least one child finishes or
@ -980,6 +980,7 @@ kj::Promise<Result<Goal::WorkResult>> DerivationGoal::buildDone(bool inBuildSlot
try {
trace("build done");
slotToken = {};
Finally releaseBuildUser([&](){ this->cleanupHookFinally(); });
cleanupPreChildKill();

2
src/libstore/build/derivation-goal.hh
View file

@ -249,7 +249,7 @@ struct DerivationGoal : public Goal
std::string key() override;
kj::Promise<Result<WorkResult>> work(bool inBuildSlot) noexcept override;
kj::Promise<Result<WorkResult>> work() noexcept override;
/**
* Add wanted outputs to an already existing derivation goal.

12
src/libstore/build/drv-output-substitution-goal.cc
View file

@ -42,7 +42,10 @@ try {
trace("trying next substituter");
if (!inBuildSlot) {
return {WaitForSlot{}};
return worker.substitutions.acquire().then([this](auto token) {
slotToken = std::move(token);
return work();
});
}
maintainRunningSubstitutions = worker.runningSubstitutions.addTemporarily(1);
@ -81,7 +84,7 @@ try {
state = &DrvOutputSubstitutionGoal::realisationFetched;
return {WaitForWorld{
pipe.promise.then([]() -> Outcome<void, Finished> { return result::success(); }), true
pipe.promise.then([]() -> Outcome<void, Finished> { return result::success(); })
}};
} catch (...) {
return {std::current_exception()};
@ -90,6 +93,7 @@ try {
kj::Promise<Result<Goal::WorkResult>> DrvOutputSubstitutionGoal::realisationFetched(bool inBuildSlot) noexcept
try {
maintainRunningSubstitutions.reset();
slotToken = {};
try {
outputInfo = downloadState->result.get();
@ -168,9 +172,9 @@ std::string DrvOutputSubstitutionGoal::key()
return "a$" + std::string(id.to_string());
}
kj::Promise<Result<Goal::WorkResult>> DrvOutputSubstitutionGoal::work(bool inBuildSlot) noexcept
kj::Promise<Result<Goal::WorkResult>> DrvOutputSubstitutionGoal::work() noexcept
{
return (this->*state)(inBuildSlot);
return (this->*state)(slotToken.valid());
}

2
src/libstore/build/drv-output-substitution-goal.hh
View file

@ -76,7 +76,7 @@ public:
std::string key() override;
kj::Promise<Result<WorkResult>> work(bool inBuildSlot) noexcept override;
kj::Promise<Result<WorkResult>> work() noexcept override;
JobCategory jobCategory() const override {
return JobCategory::Substitution;

9
src/libstore/build/goal.hh
View file

@ -1,6 +1,7 @@
#pragma once
///@file
#include "async-semaphore.hh"
#include "result.hh"
#include "types.hh"
#include "store-api.hh"
@ -112,19 +113,20 @@ struct Goal
*/
BuildResult buildResult;
protected:
AsyncSemaphore::Token slotToken;
public:
struct Finished;
struct [[nodiscard]] StillAlive {};
struct [[nodiscard]] WaitForSlot {};
struct [[nodiscard]] ContinueImmediately {};
struct [[nodiscard]] WaitForGoals {
Goals goals;
};
struct [[nodiscard]] WaitForWorld {
kj::Promise<Outcome<void, Finished>> promise;
bool inBuildSlot;
};
struct [[nodiscard]] Finished {
ExitCode exitCode;
@ -138,7 +140,6 @@ public:
struct [[nodiscard]] WorkResult : std::variant<
StillAlive,
WaitForSlot,
ContinueImmediately,
WaitForGoals,
WaitForWorld,
@ -168,7 +169,7 @@ public:
trace("goal destroyed");
}
virtual kj::Promise<Result<WorkResult>> work(bool inBuildSlot) noexcept = 0;
virtual kj::Promise<Result<WorkResult>> work() noexcept = 0;
virtual void waiteeDone(GoalPtr waitee) { }

9
src/libstore/build/local-derivation-goal.cc
View file

@ -156,8 +156,11 @@ try {
if (!inBuildSlot) {
state = &DerivationGoal::tryToBuild;
outputLocks.unlock();
if (0U != settings.maxBuildJobs) {
return {WaitForSlot{}};
if (worker.localBuilds.capacity() > 0) {
return worker.localBuilds.acquire().then([this](auto token) {
slotToken = std::move(token);
return work();
});
}
if (getMachines().empty()) {
throw Error(
@ -248,7 +251,7 @@ try {
state = &DerivationGoal::buildDone;
started();
return {WaitForWorld{std::move(promise), true}};
return {WaitForWorld{std::move(promise)}};
} catch (BuildError & e) {
outputLocks.unlock();

12
src/libstore/build/substitution-goal.cc
View file

@ -45,9 +45,9 @@ Goal::Finished PathSubstitutionGoal::done(
}
kj::Promise<Result<Goal::WorkResult>> PathSubstitutionGoal::work(bool inBuildSlot) noexcept
kj::Promise<Result<Goal::WorkResult>> PathSubstitutionGoal::work() noexcept
{
return (this->*state)(inBuildSlot);
return (this->*state)(slotToken.valid());
}
@ -203,7 +203,10 @@ try {
trace("trying to run");
if (!inBuildSlot) {
return {WaitForSlot{}};
return worker.substitutions.acquire().then([this](auto token) {
slotToken = std::move(token);
return work();
});
}
maintainRunningSubstitutions = worker.runningSubstitutions.addTemporarily(1);
@ -236,7 +239,7 @@ try {
state = &PathSubstitutionGoal::finished;
return {WaitForWorld{
pipe.promise.then([]() -> Outcome<void, Finished> { return result::success(); }), true
pipe.promise.then([]() -> Outcome<void, Finished> { return result::success(); })
}};
} catch (...) {
return {std::current_exception()};
@ -248,6 +251,7 @@ try {
trace("substitute finished");
try {
slotToken = {};
thr.get();
} catch (std::exception & e) {
printError(e.what());

2
src/libstore/build/substitution-goal.hh
View file

@ -99,7 +99,7 @@ public:
return "a$" + std::string(storePath.name()) + "$" + worker.store.printStorePath(storePath);
}
kj::Promise<Result<WorkResult>> work(bool inBuildSlot) noexcept override;
kj::Promise<Result<WorkResult>> work() noexcept override;
/**
* The states.

81
src/libstore/build/worker.cc
View file

@ -27,11 +27,13 @@ Worker::Worker(Store & store, Store & evalStore, kj::AsyncIoContext & aio)
, store(store)
, evalStore(evalStore)
, aio(aio)
/* Make sure that we are always allowed to run at least one substitution.
This prevents infinite waiting. */
, substitutions(std::max<unsigned>(1, settings.maxSubstitutionJobs))
, localBuilds(settings.maxBuildJobs)
, children(errorHandler)
{
/* Debugging: prevent recursive workers. */
nrLocalBuilds = 0;
nrSubstitutions = 0;
}
@ -210,7 +212,6 @@ void Worker::handleWorkResult(GoalPtr goal, Goal::WorkResult how)
std::visit(
overloaded{
[&](Goal::StillAlive) {},
[&](Goal::WaitForSlot) { waitForBuildSlot(goal); },
[&](Goal::ContinueImmediately) { wakeUp(goal); },
[&](Goal::WaitForGoals & w) {
for (auto & dep : w.goals) {
@ -219,9 +220,7 @@ void Worker::handleWorkResult(GoalPtr goal, Goal::WorkResult how)
}
},
[&](Goal::WaitForWorld & w) {
childStarted(
goal,
w.promise.then([](auto r) -> Result<Goal::WorkResult> {
childStarted(goal, w.promise.then([](auto r) -> Result<Goal::WorkResult> {
if (r.has_value()) {
return {Goal::ContinueImmediately{}};
} else if (r.has_error()) {
@ -229,9 +228,7 @@ void Worker::handleWorkResult(GoalPtr goal, Goal::WorkResult how)
} else {
return r.exception();
}
}),
w.inBuildSlot
);
}));
},
[&](Goal::Finished & f) { goalFinished(goal, f); },
},
@ -268,8 +265,7 @@ void Worker::wakeUp(GoalPtr goal)
}
void Worker::childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> promise,
bool inBuildSlot)
void Worker::childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> promise)
{
children.add(promise
.then([this, goal](auto result) {
@ -279,64 +275,17 @@ void Worker::childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> pr
childException = result.assume_error();
}
})
.attach(Finally{[this, goal, inBuildSlot] {
childTerminated(goal, inBuildSlot);
.attach(Finally{[this, goal] {
childTerminated(goal);
}}));
if (inBuildSlot) {
switch (goal->jobCategory()) {
case JobCategory::Substitution:
nrSubstitutions++;
break;
case JobCategory::Build:
nrLocalBuilds++;
break;
default:
abort();
}
}
}
void Worker::childTerminated(GoalPtr goal, bool inBuildSlot)
void Worker::childTerminated(GoalPtr goal)
{
if (childFinished) {
childFinished->fulfill();
}
if (inBuildSlot) {
switch (goal->jobCategory()) {
case JobCategory::Substitution:
assert(nrSubstitutions > 0);
nrSubstitutions--;
break;
case JobCategory::Build:
assert(nrLocalBuilds > 0);
nrLocalBuilds--;
break;
default:
abort();
}
}
/* Wake up goals waiting for a build slot. */
for (auto & j : wantingToBuild) {
GoalPtr goal = j.lock();
if (goal) wakeUp(goal);
}
wantingToBuild.clear();
}
void Worker::waitForBuildSlot(GoalPtr goal)
{
goal->trace("wait for build slot");
bool isSubstitutionGoal = goal->jobCategory() == JobCategory::Substitution;
if ((!isSubstitutionGoal && nrLocalBuilds < settings.maxBuildJobs) ||
(isSubstitutionGoal && nrSubstitutions < settings.maxSubstitutionJobs))
wakeUp(goal); /* we can do it right away */
else
wantingToBuild.insert(goal);
}
@ -394,16 +343,11 @@ Goals Worker::run(std::function<Goals (GoalFactory &)> req)
awake.clear();
for (auto & goal : awake2) {
checkInterrupt();
/* Make sure that we are always allowed to run at least one substitution.
This prevents infinite waiting. */
const bool inSlot = goal->jobCategory() == JobCategory::Substitution
? nrSubstitutions < std::max(1U, (unsigned int) settings.maxSubstitutionJobs)
: nrLocalBuilds < settings.maxBuildJobs;
auto result = goal->work(inSlot);
auto result = goal->work();
if (result.poll(aio.waitScope)) {
handleWorkResult(goal, result.wait(aio.waitScope).value());
} else {
childStarted(goal, std::move(result), false);
childStarted(goal, std::move(result));
}
if (topGoals.empty()) break; // stuff may have been cancelled
@ -428,7 +372,6 @@ Goals Worker::run(std::function<Goals (GoalFactory &)> req)
exited while some of its subgoals were still active. But if
--keep-going *is* set, then they must all be finished now. */
assert(!settings.keepGoing || awake.empty());
assert(!settings.keepGoing || wantingToBuild.empty());
assert(!settings.keepGoing || children.isEmpty());
return _topGoals;

32
src/libstore/build/worker.hh
View file

@ -1,6 +1,7 @@
#pragma once
///@file
#include "async-semaphore.hh"
#include "notifying-counter.hh"
#include "types.hh"
#include "lock.hh"
@ -93,22 +94,6 @@ private:
*/
WeakGoals awake;
/**
* Goals waiting for a build slot.
*/
WeakGoals wantingToBuild;
/**
* Number of build slots occupied. This includes local builds but does not
* include substitutions or remote builds via the build hook.
*/
unsigned int nrLocalBuilds;
/**
* Number of substitution slots occupied.
*/
unsigned int nrSubstitutions;
/**
* Maps used to prevent multiple instantiations of a goal for the
* same derivation / path.
@ -148,12 +133,6 @@ private:
kj::Own<kj::PromiseFulfiller<void>> childFinished;
/**
* Put `goal` to sleep until a build slot becomes available (which
* might be right away).
*/
void waitForBuildSlot(GoalPtr goal);
/**
* Wake up a goal (i.e., there is something for it to do).
*/
@ -170,16 +149,14 @@ private:
void removeGoal(GoalPtr goal);
/**
* Registers a running child process. `inBuildSlot` means that
* the process counts towards the jobs limit.
* Registers a running child process.
*/
void childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> promise,
bool inBuildSlot);
void childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> promise);
/**
* Unregisters a running child process.
*/
void childTerminated(GoalPtr goal, bool inBuildSlot);
void childTerminated(GoalPtr goal);
/**
* Pass current stats counters to the logger for progress bar updates.
@ -205,6 +182,7 @@ public:
Store & store;
Store & evalStore;
kj::AsyncIoContext & aio;
AsyncSemaphore substitutions, localBuilds;
private:
kj::TaskSet children;