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Move statvfs cache to use shared mutex

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Its read heavy and micro benchmarks show no regression on the low end
and 30%+ throughput improvements on the highend.
This commit is contained in:
Antonio SJ Musumeci
2026-05-14 00:22:06 -04:00
committed by trapexit
parent 56285fc6e5
commit 1e0bd54989
1 changed files with 24 additions and 16 deletions
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src/fs_statvfs_cache.cpp
+24 -16
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@@ -21,8 +21,8 @@
#include "fs_statvfs.hpp"
#include "statvfs_util.hpp"
#include "mutex.hpp"
#include <mutex>
#include <shared_mutex>
#include <string>
#include <unordered_map>
@@ -38,9 +38,11 @@ struct Element
typedef std::unordered_map<std::string,Element> statvfs_cache;
static u64 g_timeout = 0;
static statvfs_cache g_cache;
static Mutex g_cache_lock;
// Cache is read heavy. Use a shared mutex so concurrent reads can
// work in parallel and only inserts or refreshes take a unique lock.
static std::shared_mutex g_cache_mutex;
static u64 g_timeout = 0;
static statvfs_cache g_cache;
static
@@ -70,29 +72,35 @@ int
fs::statvfs_cache(const std::string &path_,
struct statvfs *st_)
{
int rv;
Element *e;
u64 now;
if(g_timeout == 0)
return fs::statvfs(path_,st_);
rv = 0;
now = ::_get_time();
mutex_lock(g_cache_lock);
{
std::shared_lock<std::shared_mutex> lk(g_cache_mutex);
e = &g_cache[path_];
auto it = g_cache.find(path_);
if((it != g_cache.end()) && ((now - it->second.time) <= g_timeout))
{
*st_ = it->second.st;
return 0;
}
}
if((now - e->time) > g_timeout)
int rv = 0;
std::unique_lock<std::shared_mutex> lk(g_cache_mutex);
Element &e = g_cache[path_];
if((now - e.time) > g_timeout)
{
e->time = now;
rv = fs::statvfs(path_,&e->st);
e.time = now;
rv = fs::statvfs(path_,&e.st);
}
*st_ = e->st;
mutex_unlock(g_cache_lock);
*st_ = e.st;
return rv;
}