From 4f6b92248d8ed2adf19e173b6e4824186a57ebe2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Tue, 7 Jun 2022 21:20:35 +0300
Subject: [PATCH] mdbx: add `pgop_stat.gcrtime` for collect the time spent
 loading and searching inside GC.

---
 mdbx.h          |  3 +++
 src/core.c      | 23 +++++++++++++++++++++++
 src/internals.h |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/mdbx.h b/mdbx.h
index 80eb7325..d67525cb 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -2491,6 +2491,9 @@ struct MDBX_envinfo {
     uint64_t unspill; /**< Quantity of unspilled/reloaded pages */
     uint64_t wops;    /**< Number of explicit write operations (not a pages)
                            to a disk */
+    uint64_t
+        gcrtime_seconds16dot16; /**< Time spent loading and searching inside
+                                     GC (aka FreeDB) in 1/65536 of second. */
   } mi_pgop_stat;
 };
 #ifndef __cplusplus
diff --git a/src/core.c b/src/core.c
index e150c878..efcc160c 100644
--- a/src/core.c
+++ b/src/core.c
@@ -6602,6 +6602,9 @@ page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
   unsigned re_len = MDBX_PNL_SIZE(re_list);
   pgno_t *range = nullptr;
   txnid_t oldest = 0, last = 0;
+#if MDBX_ENABLE_PGOP_STAT
+  uint64_t timestamp = 0;
+#endif /* MDBX_ENABLE_PGOP_STAT */
 
   while (true) { /* hsr-kick retry loop */
     MDBX_cursor_couple recur;
@@ -6632,6 +6635,10 @@ page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
                      ? mdbx_find_oldest(txn)
                      : atomic_load64(&env->me_lck->mti_oldest_reader,
                                      mo_AcquireRelease);
+#if MDBX_ENABLE_PGOP_STAT
+        if (likely(timestamp == 0))
+          timestamp = mdbx_osal_monotime();
+#endif /* MDBX_ENABLE_PGOP_STAT */
         ret.err = mdbx_cursor_init(&recur.outer, txn, FREE_DBI);
         if (unlikely(ret.err != MDBX_SUCCESS))
           goto fail;
@@ -6804,6 +6811,11 @@ page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
       /* Done for a kick-reclaim mode, actually no page needed */
       if (unlikely(flags & MDBX_ALLOC_SLOT)) {
         mdbx_debug("early-return NULL-page for %s mode", "MDBX_ALLOC_SLOT");
+#if MDBX_ENABLE_PGOP_STAT
+        mdbx_assert(env, timestamp != 0);
+        env->me_lck->mti_pgop_stat.gcrtime.weak +=
+            mdbx_osal_monotime() - timestamp;
+#endif /* MDBX_ENABLE_PGOP_STAT */
         ret.err = MDBX_SUCCESS;
         ret.page = NULL;
         return ret;
@@ -6942,6 +6954,11 @@ page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
     }
 
   fail:
+#if MDBX_ENABLE_PGOP_STAT
+    if (timestamp)
+      env->me_lck->mti_pgop_stat.gcrtime.weak +=
+          mdbx_osal_monotime() - timestamp;
+#endif /* MDBX_ENABLE_PGOP_STAT */
     mdbx_assert(env,
                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
@@ -6968,6 +6985,10 @@ page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
 done:
   mdbx_assert(env, !(flags & MDBX_ALLOC_SLOT));
   mdbx_ensure(env, pgno >= NUM_METAS);
+#if MDBX_ENABLE_PGOP_STAT
+  if (likely(timestamp))
+    env->me_lck->mti_pgop_stat.gcrtime.weak += mdbx_osal_monotime() - timestamp;
+#endif /* MDBX_ENABLE_PGOP_STAT */
   if (unlikely(flags & MDBX_ALLOC_FAKE)) {
     mdbx_debug("return NULL-page for %u pages %s allocation", num,
                "gc-slot/backlog");
@@ -20410,6 +20431,8 @@ __cold static int fetch_envinfo_ex(const MDBX_env *env, const MDBX_txn *txn,
         atomic_load64(&lck->mti_pgop_stat.unspill, mo_Relaxed);
     arg->mi_pgop_stat.wops =
         atomic_load64(&lck->mti_pgop_stat.wops, mo_Relaxed);
+    arg->mi_pgop_stat.gcrtime_seconds16dot16 = mdbx_osal_monotime_to_16dot16(
+        atomic_load64(&lck->mti_pgop_stat.gcrtime, mo_Relaxed));
 #else
     memset(&arg->mi_pgop_stat, 0, sizeof(arg->mi_pgop_stat));
 #endif /* MDBX_ENABLE_PGOP_STAT*/
diff --git a/src/internals.h b/src/internals.h
index 21a88711..309d3113 100644
--- a/src/internals.h
+++ b/src/internals.h
@@ -561,6 +561,9 @@ typedef struct {
   MDBX_atomic_uint64_t unspill; /* Quantity of unspilled/reloaded pages */
   MDBX_atomic_uint64_t
       wops; /* Number of explicit write operations (not a pages) to a disk */
+  MDBX_atomic_uint64_t
+      gcrtime; /* Time spending for reading/searching GC (aka FreeDB). The
+                  unit/scale is platform-depended, see mdbx_osal_monotime(). */
 } MDBX_pgop_stat_t;
 #endif /* MDBX_ENABLE_PGOP_STAT */