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Merge pull request #13478 from NixOS/posix-source-accessor-concurrent-map

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PosixSourceAccessor: Use concurrent_flat_map
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Eelco Dolstra 2025-07-24 11:19:37 +02:00 • committed by GitHub
commit cbdb497c79
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1 changed files with 10 additions and 12 deletions
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22
src/libutil/posix-source-accessor.cc
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@ -3,7 +3,7 @@
#include "nix/util/signals.hh"
#include "nix/util/sync.hh"
#include <unordered_map>
#include <boost/unordered/concurrent_flat_map.hpp>
namespace nix {
@ -88,25 +88,23 @@ bool PosixSourceAccessor::pathExists(const CanonPath & path)
std::optional<struct stat> PosixSourceAccessor::cachedLstat(const CanonPath & path)
{
static SharedSync<std::unordered_map<Path, std::optional<struct stat>>> _cache;
using Cache = boost::concurrent_flat_map<Path, std::optional<struct stat>>;
static Cache cache;
// Note: we convert std::filesystem::path to Path because the
// former is not hashable on libc++.
Path absPath = makeAbsPath(path).string();
{
auto cache(_cache.readLock());
auto i = cache->find(absPath);
if (i != cache->end())
return i->second;
}
std::optional<Cache::mapped_type> res;
cache.cvisit(absPath, [&](auto & x) { res.emplace(x.second); });
if (res)
return *res;
auto st = nix::maybeLstat(absPath.c_str());
auto cache(_cache.lock());
if (cache->size() >= 16384)
cache->clear();
cache->emplace(absPath, st);
if (cache.size() >= 16384)
cache.clear();
cache.emplace(absPath, st);
return st;
}