From 5927385942c950048df3143651f72ec27ce7be31 Mon Sep 17 00:00:00 2001
From: Jeremy Maitin-Shepard <jbms@google.com>
Date: Tue, 22 Oct 2024 21:12:14 -0700
Subject: [PATCH] Reduce contention on cache hash table mutex

Previously, the mutex was unnecessarily held while destroying cache
entries in the case that `total_bytes_limit == 0`, leading to contention
on the mutex in the case that destruction is expensive (e.g. release a
large memory allocation).

PiperOrigin-RevId: 688801635
Change-Id: I347f5c6312920bb6b4ae4b3396dbd6414654dfaa
---
 tensorstore/internal/cache/cache.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tensorstore/internal/cache/cache.cc b/tensorstore/internal/cache/cache.cc
index 317755a9f..454f8db6b 100644
--- a/tensorstore/internal/cache/cache.cc
+++ b/tensorstore/internal/cache/cache.cc
@@ -362,6 +362,9 @@ void StrongPtrTraitsCacheEntry::decrement_impl(
           cache->reference_count_.fetch_sub(CacheImpl::kNonEmptyShardIncrement,
                                             std::memory_order_relaxed);
         }
+        // Release lock before invoking entry destructor, as that may be
+        // expensive.
+        lock = {};
         delete entry_impl;
       }
     } else {