diff mbox series

malloc: send freed small chunks to smallbin

Message ID hiiYem_ZNqLRZITFGxNDKtkjhFsdE7PRwCnk5Ub7A-H5ydgO1y3OriCNc48lbp_8sNVKQDiuTotTLEVGM9AHWL90nxacD_SwRT67nuoao-8=@proton.me
State New
Headers show
Series malloc: send freed small chunks to smallbin | expand

Commit Message

k4lizen July 7, 2024, 5:09 a.m. UTC 
Large chunks get added to the unsorted bin since
sorting them takes time, for small chunks the
benefit of adding them to the unsorted bin is
non-existant, actually hurting performance.

Splitting and malloc_consolidate still add small
chunks to unsorted, but we can hint the compiler
that that is a relatively rare occurance.
Benchmarking shows this to be consistently good.
---
 malloc/malloc.c | 51 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 17 deletions(-)
diff mbox series

Patch

diff --git a/malloc/malloc.c b/malloc/malloc.c
index bcb6e5b83c..14b0866194 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4156,9 +4156,9 @@  _int_malloc (mstate av, size_t bytes)
 #endif
             }
 
-          /* place chunk in bin */
-
-          if (in_smallbin_range (size))
+          /* Place chunk in bin. Only malloc_consolidate() and splitting can put
+      small chunks into the unsorted bin. */
+          if (__glibc_unlikely (in_smallbin_range (size)))
             {
               victim_index = smallbin_index (size);
               bck = bin_at (av, victim_index);
@@ -4723,23 +4723,41 @@  _int_free_create_chunk (mstate av, mchunkptr p, INTERNAL_SIZE_T size,
       } else
 	clear_inuse_bit_at_offset(nextchunk, 0);
 
+      mchunkptr bck, fwd;
+
+      if(in_smallbin_range (size)){
       /*
-	Place the chunk in unsorted chunk list. Chunks are
-	not placed into regular bins until after they have
-	been given one chance to be used in malloc.
+  Place small chunks directly in their smallbin, so they
+  don't pollute the unsorted bin.
       */
 
-      mchunkptr bck = unsorted_chunks (av);
-      mchunkptr fwd = bck->fd;
-      if (__glibc_unlikely (fwd->bk != bck))
-	malloc_printerr ("free(): corrupted unsorted chunks");
-      p->fd = fwd;
+        int chunk_index = smallbin_index (size);
+        bck = bin_at (av, chunk_index);
+        fwd = bck->fd;
+
+        if (__glibc_unlikely (fwd->bk != bck))
+    malloc_printerr ("free(): chunks in smallbin corrupted");
+
+        mark_bin (av, chunk_index);
+      }
+      else
+      {
+      /*
+  Place large chunks in unsorted chunk list. Large chunks are
+  not placed into regular bins until after they have
+  been given one chance to be used in malloc.
+      */
+
+        bck = unsorted_chunks (av);
+        fwd = bck->fd;
+        if (__glibc_unlikely (fwd->bk != bck))
+    malloc_printerr ("free(): corrupted unsorted chunks");
+        p->fd_nextsize = NULL;
+        p->bk_nextsize = NULL;
+      }
+      
       p->bk = bck;
-      if (!in_smallbin_range(size))
-	{
-	  p->fd_nextsize = NULL;
-	  p->bk_nextsize = NULL;
-	}
+      p->fd = fwd;
       bck->fd = p;
       fwd->bk = p;
 
@@ -4748,7 +4766,6 @@  _int_free_create_chunk (mstate av, mchunkptr p, INTERNAL_SIZE_T size,
 
       check_free_chunk(av, p);
     }
-
   else
     {
       /* If the chunk borders the current high end of memory,