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[generator:preprocess] Optimize o5m reading: aggressive readahead

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Anatoly Serdtcev 2019-11-11 15:59:02 +03:00 • committed by LaGrunge
parent 1c62760907
commit 7c4744f0ae
1 changed files with 6 additions and 1 deletions
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7
generator/osm_source.cpp
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@ -15,6 +15,7 @@
#include "base/file_name_utils.hpp"
#include <fstream>
#include <future>
#include <memory>
#include <set>
#include <thread>
@ -253,7 +254,11 @@ void BuildIntermediateDataFromO5M(
auto sourceMap = boost::iostreams::mapped_file_source{filename};
if (!sourceMap.is_open())
MYTHROW(Writer::OpenException, ("Failed to open", filename));
::madvise(const_cast<char*>(sourceMap.data()), sourceMap.size(), MADV_SEQUENTIAL);
// Try aggressively (MADV_WILLNEED) and asynchronously (std::launch::async) read ahead
// the o5m-file.
std::async(std::launch::async, [data = sourceMap.data(), size = sourceMap.size()] {
::madvise(const_cast<char*>(data), size, MADV_WILLNEED);
});
constexpr size_t chunkSize = 10'000;
std::vector<std::thread> threads;