MonetDB: Jun2023 - Do handing over of free list more efficiently.

[Sjoerd Mullender via checkin-list]

Changeset: b5759233e564 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/b5759233e564
Modified Files:
        gdk/gdk_bbp.c
Branch: Jun2023
Log Message:

Do handing over of free list more efficiently.


diffs (65 lines):

diff --git a/gdk/gdk_bbp.c b/gdk/gdk_bbp.c
--- a/gdk/gdk_bbp.c
+++ b/gdk/gdk_bbp.c
@@ -2559,18 +2559,34 @@ BBPuncacheit(bat i, bool unloaddesc)
  * BBPclear removes a BAT from the BBP directory forever.
  */
 static inline void
-BBPhandover(Thread t)
+BBPhandover(Thread t, int n)
 {
        /* take one bat from our private free list and hand it over to
         * the global free list */
        bat i = t->freebats;
+       bat bid = i;
+       if (i == 0)
+               return;
+       for (int j = 1; j < n; j++) {
+               if (BBP_next(i) == 0) {
+                       n = j;
+                       break;
+               }
+               i = BBP_next(i);
+       }
        t->freebats = BBP_next(i);
-       t->nfreebats--;
-       bat *p;
-       for (p = &BBP_free; *p && *p < i; p = &BBP_next(*p))
-               ;
-       BBP_next(i) = *p;
-       *p = i;
+       t->nfreebats -= n;
+       BBP_next(i) = 0;
+       bat *p = &BBP_free;
+       while (n > 0) {
+               while (*p && *p < bid)
+                       p = &BBP_next(*p);
+               i = BBP_next(bid);
+               BBP_next(bid) = *p;
+               *p = bid;
+               bid = i;
+               n--;
+       }
 }
 
 static inline void
@@ -2609,9 +2625,7 @@ bbpclear(bat i, bool lock)
        if (t->nfreebats > BBP_FREE_HIWATER) {
                if (lock)
                        MT_lock_set(&GDKcacheLock);
-               while (t->nfreebats > BBP_FREE_LOWATER) {
-                       BBPhandover(t);
-               }
+               BBPhandover(t, t->nfreebats - BBP_FREE_LOWATER);
                if (lock)
                        MT_lock_unset(&GDKcacheLock);
        }
@@ -2633,7 +2647,7 @@ BBPrelinquish(Thread t)
                return;
        MT_lock_set(&GDKcacheLock);
        while (t->nfreebats > 0) {
-               BBPhandover(t);
+               BBPhandover(t, t->nfreebats);
        }
        MT_lock_unset(&GDKcacheLock);
 }
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