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Don't retain SharedDataFacade between queries (#3485)

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* Don't retain SharedDataFacade between queries

* More caching code
This commit is contained in:
Patrick Niklaus 2017-01-03 12:06:55 +01:00 committed by Michael Krasnyk
parent 2ed6b181c8
commit f7ad2e1e26
1 changed files with 38 additions and 17 deletions
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55
include/engine/data_watchdog.hpp
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@ -22,11 +22,6 @@ namespace engine
// This class monitors the shared memory region that contains the pointers to
// the data and layout regions that should be used. This region is updated
// once a new dataset arrives.
//
// TODO: This also needs a shared memory reader lock with other clients and
// possibly osrm-datastore since updating the CURRENT_REGIONS data is not atomic.
// Currently we enfore this by waiting that all queries have finished before
// osrm-datastore writes to this section.
class DataWatchdog
{
public:
@ -57,7 +52,9 @@ class DataWatchdog
const auto shared_timestamp =
static_cast<const storage::SharedDataTimestamp *>(shared_regions->Ptr());
const auto get_locked_facade = [this, shared_timestamp]() {
const auto get_locked_facade = [this, shared_timestamp](
const std::shared_ptr<datafacade::SharedMemoryDataFacade> &facade) {
if (current_timestamp.region == storage::REGION_1)
{
return std::make_pair(RegionsLock(shared_barriers->region_1_mutex), facade);
@ -76,8 +73,11 @@ class DataWatchdog
if (shared_timestamp->timestamp == current_timestamp.timestamp)
{
BOOST_ASSERT(shared_timestamp->region == current_timestamp.region);
return get_locked_facade();
if (auto facade = cached_facade.lock())
{
BOOST_ASSERT(shared_timestamp->region == current_timestamp.region);
return get_locked_facade(facade);
}
}
}
@ -89,20 +89,41 @@ class DataWatchdog
// in that case we don't modify anything
if (shared_timestamp->timestamp == current_timestamp.timestamp)
{
BOOST_ASSERT(shared_timestamp->region == current_timestamp.region);
return get_locked_facade();
if (auto facade = cached_facade.lock())
{
BOOST_ASSERT(shared_timestamp->region == current_timestamp.region);
return get_locked_facade(facade);
}
}
// this thread has won and can update the data
boost::upgrade_to_unique_lock<boost::upgrade_mutex> unique_facade_lock(facade_lock);
current_timestamp = *shared_timestamp;
facade = std::make_shared<datafacade::SharedMemoryDataFacade>(shared_barriers,
current_timestamp.region,
current_timestamp.timestamp);
// if two threads try to enter this critical section one will loose
// and will find an up-to-date instance of the shared data facade
if (shared_timestamp->timestamp == current_timestamp.timestamp)
{
// if the thread that updated the facade finishes the query before
// we can aquire our handle here, we need to regenerate
if (auto facade = cached_facade.lock())
{
BOOST_ASSERT(shared_timestamp->region == current_timestamp.region);
return get_locked_facade();
return get_locked_facade(facade);
}
}
else
{
current_timestamp = *shared_timestamp;
}
auto new_facade =
std::make_shared<datafacade::SharedMemoryDataFacade>(shared_barriers,
current_timestamp.region,
current_timestamp.timestamp);
cached_facade = new_facade;
return get_locked_facade(new_facade);
}
private:
@ -114,7 +135,7 @@ class DataWatchdog
std::unique_ptr<storage::SharedMemory> shared_regions;
mutable boost::shared_mutex facade_mutex;
std::shared_ptr<datafacade::SharedMemoryDataFacade> facade;
std::weak_ptr<datafacade::SharedMemoryDataFacade> cached_facade;
storage::SharedDataTimestamp current_timestamp;
};
}