⚡ Bolt: Optimize KernelDirectMemoryQuery direct allocations LINQ query

.jules/bolt.md

@@ -48,3 +48,8 @@
 **Context:** Guest MMU / `VirtualMemory.cs` (`CopyFromRegions`, `CopyToRegions`)
 **Learning:** Sequential tracking over Spans with an external `copied` counter and range indexer (`span[copied..]`) introduces local bounds check validation overhead. Reassigning the span reference in place via `span = span.Slice(chunkLength)` eliminates this and simplifies hot loops into `!span.IsEmpty` checks.
 **Action:** Use idiomatic slice-reassignment (`span = span.Slice(length)`) instead of external integer trackers in loop conditions over `Span<T>` sequential memory operations to reduce arithmetic overhead.
+
+## 2026-10-06 - Zero-Allocation Search in KernelMemoryCompatExports
+**Context:** src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
+**Learning:** Found an O(N log N) LINQ-based sorting/filtering bottleneck (`.Values.Where(...).OrderBy(...)`) inside the `KernelDirectMemoryQuery` lock. This was causing GC pressure due to enumerator and delegate allocations on a hot path during kernel HLE queries.
+**Action:** Replaced it with an O(N) allocation-free manual search loop using standard variables (`matchStart`, `matchEnd`) to natively handle uniqueness and prioritization.

src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs

@@ -3706,19 +3706,23 @@ public static int KernelDirectMemoryQuery(CpuContext ctx)
 
         lock (_memoryGate)
         {
-            var candidates = _directAllocations.Values
-                .Where(block => findNext
+            // Performance optimization: Replaced O(N log N) LINQ sorting and allocating Where/OrderBy chain with a single-pass O(N) allocation-free manual search loop.
+            foreach (var block in _directAllocations.Values)
+            {
+                var isMatch = findNext
                     ? block.Start + block.Length > offset
-                    : offset >= block.Start && offset < block.Start + block.Length)
-                .OrderBy(block => block.Start);
+                    : offset >= block.Start && offset < block.Start + block.Length;
 
-            foreach (var block in candidates)
-            {
-                found = true;
-                matchStart = block.Start;
-                matchEnd = block.Start + block.Length;
-                matchMemoryType = block.MemoryType;
-                break;
+                if (isMatch)
+                {
+                    if (!found || block.Start < matchStart)
+                    {
+                        found = true;
+                        matchStart = block.Start;
+                        matchEnd = block.Start + block.Length;
+                        matchMemoryType = block.MemoryType;
+                    }
+                }
             }
         }