From: Cupertino Miranda <cupertino.miranda@oracle.com>
Date: Wed, 16 Apr 2025 11:22:53 +0000 (+0000)
Subject: malloc: move tcache_init out of hot tcache paths
X-Git-Tag: glibc-2.42~297
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1c9ac027a5deb6c3e026be0e88d38959529e6102;p=thirdparty%2Fglibc.git

malloc: move tcache_init out of hot tcache paths

This patch moves any calls of tcache_init away after tcache hot paths.
Since there is no reason to initialize tcaches in the hot path and since
we need to be able to check tcache != NULL in any case, because of
tcache_thread_shutdown function, moving tcache_init away from hot path
can only be beneficial.
The patch also removes the initialization of tcaches within the
__libc_free call. It only makes sense to initialize tcaches for the
thread after it calls one of the allocation functions. Also the patch
removes the save/restore of errno from tcache_init code, as it is no
longer needed.
---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index f30fb4b1ba..23b9306a19 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3296,9 +3296,6 @@ tcache_init(void)
   if (MAX_TCACHE_SIZE >= GLRO (dl_pagesize) / 2)
     malloc_printerr ("max tcache size too large");
 
-  /* Preserve errno when called from free() - _int_malloc may corrupt it.  */
-  int err = errno;
-
   arena_get (ar_ptr, bytes);
   victim = _int_malloc (ar_ptr, bytes);
   if (!victim && ar_ptr != NULL)
@@ -3311,8 +3308,6 @@ tcache_init(void)
   if (ar_ptr != NULL)
     __libc_lock_unlock (ar_ptr->mutex);
 
-  __set_errno (err);
-
   /* In a low memory situation, we may not be able to allocate memory
      - in which case, we just keep trying later.  However, we
      typically do this very early, so either there is sufficient
@@ -3346,13 +3341,15 @@ tcache_try_malloc (size_t bytes, void **memptr)
 
   size_t tc_idx = csize2tidx (tbytes);
 
-  MAYBE_INIT_TCACHE ();
-
   if (tcache_available (tc_idx))
-    *memptr = tcache_get (tc_idx);
+    {
+      *memptr = tcache_get (tc_idx);
+      return false;
+    }
   else
     *memptr = NULL;
 
+  MAYBE_INIT_TCACHE ();
   return false;
 }
 
@@ -3684,8 +3681,6 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
       }
     size_t tc_idx = csize2tidx (tbytes);
 
-    MAYBE_INIT_TCACHE ();
-
     if (tcache_available (tc_idx))
       {
 	/* The tcache itself isn't encoded, but the chain is.  */
@@ -3702,6 +3697,7 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
 	    return tag_new_usable (victim);
 	  }
       }
+    MAYBE_INIT_TCACHE ();
   }
 #endif
 
@@ -4556,8 +4552,6 @@ _int_free_chunk (mstate av, mchunkptr p, INTERNAL_SIZE_T size, int have_lock)
 {
   mfastbinptr *fb;             /* associated fastbin */
 
-  MAYBE_INIT_TCACHE ();
-
   /*
     If eligible, place chunk on a fastbin so it can be found
     and used quickly in malloc.