Add PID information to -LL_miss_file output (#6896)

When using simulator parameters -LL_miss_file option, I noticed that the
output was insufficient for detailed analysis, especially when
distinguishing cache misses across processes. This limitation becomes
more apparent in environments where multiple processes may experience
cache misses at similar virtual memory addresses, potentially leading to
ambiguous outputs.

So, I have updated the dump_miss function within
caching_device_stats.cpp to include the PID in the output. This small
yet impactful change ensures that each cache miss log entry is prefixed
with the PID of the process, thereby enabling users to better correlate
the cache misses with specific processes.

api/docs/release.dox

@@ -161,6 +161,8 @@ changes:
    signature between AArch64 and RISC-V.
  - Renamed dr_get_sve_vector_length() to dr_get_vector_length() to share function
    signature between AArch64 and RISC-V.
+ - Changed the drcachesim -LL_miss_file option by adding a process ID field to the output.
+   This helps in better analyzing cache misses in multi-process environments.
 
 Further non-compatibility-affecting changes include:
  - Added DWARF-5 support to the drsyms library by linking in 4 static libraries

clients/drcachesim/common/options.cpp

@@ -208,11 +208,11 @@ droption_t<std::string> op_LL_miss_file(
     "Path for dumping LLC misses or prefetching hints",
     "If non-empty, when running the cache simulator, requests that "
     "every last-level cache miss be written to a file at the specified path. Each miss "
-    "is written in text format as a <program counter, address> pair. If this tool is "
-    "linked with zlib, the file is written in gzip-compressed format. If non-empty, when "
-    "running the cache miss analyzer, requests that prefetching hints based on the miss "
-    "analysis be written to the specified file. Each hint is written in text format as a "
-    "<program counter, stride, locality level> tuple.");
+    "is written in text format as a <process id, program counter, address> tuple. If "
+    "this tool is linked with zlib, the file is written in gzip-compressed format. If "
+    "non-empty, when running the cache miss analyzer, requests that prefetching hints "
+    "based on the miss analysis be written to the specified file. Each hint is written "
+    "in text format as a <program counter, stride, locality level> tuple.");
 
 droption_t<bool> op_L0_filter_deprecated(
     DROPTION_SCOPE_CLIENT, "L0_filter", false,

clients/drcachesim/simulator/cache_miss_analyzer.cpp

@@ -83,6 +83,8 @@ cache_miss_stats_t::dump_miss(const memref_t &memref)
         return;
     }
 
+    // TODO i#6905: Consider incorporating PID information into the pc_cache_misses_ hash
+    // map and adjusting subsequent calculations that depend on this data.
     const addr_t pc = memref.data.pc;
     const addr_t addr = memref.data.addr / kLineSize;
     pc_cache_misses_[pc].push_back(addr);

clients/drcachesim/simulator/caching_device_stats.cpp

@@ -154,6 +154,7 @@ void
 caching_device_stats_t::dump_miss(const memref_t &memref)
 {
     addr_t pc, addr;
+    memref_pid_t pid;
     if (type_is_instr(memref.instr.type))
         pc = memref.instr.addr;
     else { // data ref: others shouldn't get here
@@ -163,10 +164,15 @@ caching_device_stats_t::dump_miss(const memref_t &memref)
         pc = memref.data.pc;
     }
     addr = memref.data.addr;
+    pid = memref.data.pid;
+
+    // XXX: This writing method to the same file from multiple processes is racy.
+    // It works most of the time but consider using a directory with individual files
+    // per process as a future safer alternative.
 #ifdef HAS_ZLIB
-    gzprintf(file_, "0x%zx,0x%zx\n", pc, addr);
+    gzprintf(file_, "%lld,0x%zx,0x%zx\n", pid, pc, addr);
 #else
-    fprintf(file_, "0x%zx,0x%zx\n", pc, addr);
+    fprintf(file_, "%lld,0x%zx,0x%zx\n", pid, pc, addr);
 #endif
 }