* Use min-heap for EventCache.SortAndDispatch

Replace the O(N*T) linear-scan merge in SortAndDispatch with an O(N*log(T))
min-heap merge, where N is the number of events and T is the number of
threads. The previous implementation rebuilt a List from LINQ on every call
and linearly scanned all thread queues for the minimum timestamp per event.

The new implementation uses an array-backed binary min-heap keyed by
timestamp. After extracting the minimum, only a single O(log T) sift-down
is needed to restore the heap property. The heap list is reused across
calls to avoid per-call allocations.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Track active thread queues in EventCache.SortAndDispatch

Maintain a HashSet of thread queues that have pending events instead of
iterating all threads in the dictionary on every SortAndDispatch call.
Queues are added to the active set when their first event is enqueued
and removed when drained. This eliminates the Dictionary.Values
enumeration which was ~28% of CPU during nettrace-to-TraceLog conversion.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Cache ParsedSymbolMetadata to avoid repeated JSON deserialization

Cache the result of ProcessMappingSymbolMetadataParser.TryParse() in
ProcessMappingMetadataTraceData so that repeated accesses to the
ParsedSymbolMetadata property do not re-invoke JSON deserialization.
The property is accessed twice per mapping event (for PE and ELF
metadata checks), and the metadata objects are shared across multiple
mappings via MetadataId. This was ~10% of CPU during conversion.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Avoid redundant FileName string allocations in ProcessMapping handler

Read ProcessMappingTraceData.FileName once into a local variable and pass
it directly to UniversalMapping(string, ...) instead of going through the
UniversalMapping(ProcessMappingTraceData, ...) overload. Previously,
FileName was accessed 3 times per mapping event (IsNullOrEmpty check,
StartsWith check, and inside UniversalMapping), each time allocating a
new string via GetShortUTF8StringAt(). String allocation was ~12% of CPU
in Release-mode profiling.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Reset ParsedSymbolMetadata cache in Dispatch to prevent stale data

TraceEvent objects are reused across callbacks. The cached
ParsedSymbolMetadata fields were never cleared between dispatches,
which could return metadata from a previous event if the property
was accessed on the template object rather than a clone.

Reset _parsedSymbolMetadataCached and _parsedSymbolMetadata at the
start of Dispatch() before invoking the callback.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address code review feedback: MinHeap class, Clone override, comments

Refactor the min-heap helpers into a self-contained private MinHeap
class with XML doc comments on all public methods. Add comments
explaining the binary heap child index formulas (2i+1, 2i+2). Use
C# tuple swap syntax instead of a temp variable.

Add Clone() override to ProcessMappingMetadataTraceData to explicitly
copy the cached ParsedSymbolMetadata fields into the clone. Strings
are immutable so a shallow copy of the reference is sufficient.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add MinHeap unit tests and improve Build() comment

Make MinHeap generic (MinHeap) and internal so it can be
tested from the test project. Add 13 unit tests covering: empty heap,
single element, ascending/descending/random input, duplicate keys,
ReplaceRoot, RemoveRoot, Clear, and mixed operations. Add a comment
to Build() explaining why iteration starts at Count/2-1.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…2404)

System.Text.Json 9.0.8 has transitive dependencies on System.IO.Pipelines
and Microsoft.Bcl.AsyncInterfaces that were not being embedded in the
self-extracting PerfView EXE. When these DLLs are absent at runtime,
System.Text.Json fails to parse ProcessMappingMetadata JSON, causing all
ELF and PE module binary formats to be reported as Unknown. This prevents
symbol resolution for Linux .nettrace traces.

Add both packages to Directory.Packages.props and embed them as resources
in PerfView.csproj alongside the existing System.Text.Json dependencies.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/perfview/sessions/78f533da-c8ef-489d-ac6c-05e8d856413a

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: brianrob <6210322+brianrob@users.noreply.github.com>