[llvm] 35a003c - [MemProf][NFC] Clear each IndexedMemProfRecord after it is written (#75205)

[via llvm-commits]

Author: Teresa Johnson
Date: 2023-12-15T11:38:33-08:00
New Revision: 35a003c2b21082f3c47c8b01d9d1955af5ab098e

URL: https://github.com/llvm/llvm-project/commit/35a003c2b21082f3c47c8b01d9d1955af5ab098e
DIFF: https://github.com/llvm/llvm-project/commit/35a003c2b21082f3c47c8b01d9d1955af5ab098e.diff

LOG: [MemProf][NFC] Clear each IndexedMemProfRecord after it is written (#75205)

The on-disk hash table for the memprof writer holds copies of all the
memprof records to be written. These hold a lot of memory in aggregate,
due to the lists of alloc sites (which each have a list of context
frames) and call sites. Clear each one after emitting it.

This drops the peak memory when writing a very large indexed memprof
profile by about 2.5G.

Added: 
    

Modified: 
    llvm/include/llvm/ProfileData/MemProf.h
    llvm/lib/ProfileData/InstrProfWriter.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ProfileData/MemProf.h b/llvm/include/llvm/ProfileData/MemProf.h
index 6557481870d8c2..37c19094bc2a63 100644
--- a/llvm/include/llvm/ProfileData/MemProf.h
+++ b/llvm/include/llvm/ProfileData/MemProf.h
@@ -538,6 +538,11 @@ class RecordWriterTrait {
                 offset_type /*Unused*/) {
     assert(Schema != nullptr && "MemProf schema is not initialized!");
     V.serialize(*Schema, Out);
+    // Clear the IndexedMemProfRecord which results in clearing/freeing its
+    // vectors of allocs and callsites. This is owned by the associated on-disk
+    // hash table, but unused after this point. See also the comment added to
+    // the client which constructs the on-disk hash table for this trait.
+    V.clear();
   }
 };
 

diff  --git a/llvm/lib/ProfileData/InstrProfWriter.cpp b/llvm/lib/ProfileData/InstrProfWriter.cpp
index 68b77a1482976a..d65f8fe50313dc 100644
--- a/llvm/lib/ProfileData/InstrProfWriter.cpp
+++ b/llvm/lib/ProfileData/InstrProfWriter.cpp
@@ -539,6 +539,9 @@ Error InstrProfWriter::writeImpl(ProfOStream &OS) {
     // Release the memory of this MapVector as it is no longer needed.
     MemProfRecordData.clear();
 
+    // The call to Emit invokes RecordWriterTrait::EmitData which destructs
+    // the memprof record copies owned by the RecordTableGenerator. This works
+    // because the RecordTableGenerator is not used after this point.
     uint64_t RecordTableOffset =
         RecordTableGenerator.Emit(OS.OS, *RecordWriter);