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perf: defer SharedInfo allocation in ClassInfoCache.share() #68

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perf: defer SharedInfo allocation in ClassInfoCache.share() #68

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7 changes: 3 additions & 4 deletions utils/src/main/java/datadog/instrument/utils/ClassInfoCache.java
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Original file line number Diff line number Diff line change
Expand Up @@ -181,9 +181,6 @@ public void share(String className, T info, int classLoaderKeyId) {
final SharedInfo[] shared = this.shared;
final int slotMask = this.slotMask;

// always wrap info in a new wrapper to avoid consistency issues
final SharedInfo update = new SharedInfo(className, info, classLoaderKeyId);

int oldestTick = Integer.MAX_VALUE;
int oldestSlot = -1;

Expand All @@ -192,7 +189,7 @@ public void share(String className, T info, int classLoaderKeyId) {
for (int i = 1, h = hash; true; i++, h = rehash(h)) {
int slot = slotMask & h;
SharedInfo existing = shared[slot];
if (existing != null && !existing.equals(update)) {
if (existing != null && !existing.className.equals(className)) {
// slot already used by a different class
int tick = existing.accessed;
if (i < MAX_HASH_ATTEMPTS) {
Expand All @@ -211,6 +208,8 @@ public void share(String className, T info, int classLoaderKeyId) {
// last hashed slot is least-recently-used, re-use it
}
}
// wrap info in a new wrapper (deferred to avoid allocation on early match)
SharedInfo update = new SharedInfo(className, info, classLoaderKeyId);
shared[slot] = update;
// increment global TICKS whenever info is shared
// avoid incrementing it in 'find' for performance reasons
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