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fix(codecache): report the real runtime-stubs cache size #681

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fix(codecache): report the real runtime-stubs cache size #681

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bb2147f
fix(codecache): report the real runtime-stubs cache size
rkennke Jul 22, 2026
2886d41
docs(codecache): word runtime-stubs usage as approximate, not "live f…
rkennke Jul 22, 2026
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7 changes: 7 additions & 0 deletions ddprof-lib/src/main/cpp/hotspot/jitCodeCache.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -52,3 +52,10 @@ CodeBlob* JitCodeCache::findRuntimeStub(const void *address) {
_stubs_lock.unlockShared();
return stub;
}

long long JitCodeCache::runtimeStubsMemoryUsage() {
_stubs_lock.lockShared();
long long usage = _runtime_stubs.memoryUsage();
_stubs_lock.unlockShared();
return usage;
}
6 changes: 6 additions & 0 deletions ddprof-lib/src/main/cpp/hotspot/jitCodeCache.h
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Expand Up @@ -38,6 +38,12 @@ class JitCodeCache {
}

static CodeBlob* findRuntimeStub(const void *address);

// Approximate heap usage of the runtime-stubs code cache, via
// CodeCache::memoryUsage() (a capacity/count-based estimate today; #677
// makes it exact). Read under the shared stubs lock because
// DynamicCodeGenerated() mutates _runtime_stubs (add()/expand()) concurrently.
static long long runtimeStubsMemoryUsage();
static bool isJitCode(const void* pc) {
return CodeHeap::contains(pc);
}
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6 changes: 5 additions & 1 deletion ddprof-lib/src/main/cpp/profiler.cpp
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Expand Up @@ -21,6 +21,7 @@
#include "itimer.h"
#include "hotspot/vmStructs.inline.h"
#include "hotspot/hotspotSupport.h"
#include "hotspot/jitCodeCache.h"
#include "j9/j9Support.h"
#include "j9/j9WallClock.h"
#include "jvmSupport.h"
Expand Down Expand Up @@ -1737,8 +1738,11 @@ Error Profiler::dump(const char *path, const int length) {
const CodeCacheArray& native_libs = _libs->native_libs();
Counters::set(CODECACHE_NATIVE_COUNT, native_libs.count());
Counters::set(CODECACHE_NATIVE_SIZE_BYTES, native_libs.memoryUsage());
// The runtime-stubs counter reflects the JIT runtime-stubs code cache, a
// separate cache from the native libraries (it previously duplicated
// native_libs.memoryUsage() by copy-paste). Read under its shared lock.
Counters::set(CODECACHE_RUNTIME_STUBS_SIZE_BYTES,
native_libs.memoryUsage());
JitCodeCache::runtimeStubsMemoryUsage());

Error err = Error::OK;
// rotateDictsAndRun rotates the dictionaries, takes lockAll() around the
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