Negative numbers in the stats (v.2.24)

[davide-digennaro-nozomi]

in our interactive server, the mem command will execute

  size_t current = 0, peak = 0;
  mi_process_info(nullptr, nullptr, nullptr, &current, &peak, nullptr, nullptr, nullptr);

and the mem full command does (pseudo-code)

ask each thread to execute:
      mi_collect(false); mi_collect(true); mi_stats_merge();

return mi_stats_get_json

Here's a session, where we typed mem, mem full, mem all in a row (the server was running, but the entire test took less than 2 seconds).

# mem
{"current":"262270976", "peak":"1164668928", ...}

# mem full

[{
  "version": 1,
  "mimalloc_version": 224,
  "process": {
    "elapsed_msecs": 335944,
    "user_msecs": 88246,
    "system_msecs": 60148,
    "page_faults": 3317,
    "rss_current": 18446744073468309504,   <====
    "rss_peak": 1198329856,
    "commit_current": 18446744073468309504,   <====
    "commit_peak": 979955712
  },
  "pages": { "total": 0, "peak": 0, "current": -14417 },
  "reserved": { "total": 2554785792, "peak": 2554785792, "current": 2554785792 },
  "committed": { "total": 1491464192, "peak": 979955712, "current": -241242112 },   <====
  "reset": { "total": 0, "peak": 0, "current": 0 },
  "purged": { "total": 1714290688, "peak": 1714290688, "current": 1714290688 },
  "page_committed": { "total": 3145728, "peak": 1699856, "current": -2557365280 },
  "pages_abandoned": { "total": 24, "peak": 24, "current": 8 },
  "threads": { "total": 42, "peak": 37, "current": 37 },
  "malloc_normal": { "total": 0, "peak": 0, "current": 0 },
  "malloc_huge": { "total": 2262679552, "peak": 2262679552, "current": 2262679552 },
  "malloc_requested": { "total": 0, "peak": 0, "current": 0 },
  "mmap_calls": 40,
  "commit_calls": 1447,
  "reset_calls": 0,
  "purge_calls": 1676,
  "arena_count": 2,
  "malloc_normal_count": 0,
  "malloc_huge_count": 2450,
  "malloc_guarded_count": 0,
  "arena_rollback_count": 0,
  "arena_purges": 25,
  "pages_extended": 0,
  "pages_retire": 0,
  "page_searches": 0,
  "segments": { "total": 51, "peak": 50, "current": 42 },
  "segments_abandoned": { "total": 4, "peak": 4, "current": 1 },
...  
"page_bins": [
    { "total": 0, "peak": 0, "current": 0, "block_size": 8, "page_size": 65536 },
    { "total": 0, "peak": 0, "current": -21, "block_size": 8, "page_size": 65536 },
    { "total": 0, "peak": 0, "current": -183, "block_size": 16, "page_size": 65536 },
    { "total": 0, "peak": 0, "current": 0, "block_size": 24, "page_size": 65536 },
    { "total": 0, "peak": 0, "current": -98, "block_size": 32, "page_size": 65536 },
...
  ]
}

# mem
{"current":"18446744072832557056", "peak":"1249579008"...}

so current was initially ok, it became negative after mi_collect (but we don't know if there is a causality relationship), and after it gets negative, it never resets.