xmalloc_tlsf: Fall back to xmalloc_whole_pages() if xmem_pool_alloc() fails.

This was happening for xmalloc request sizes between 3921 and 3951
bytes. The reason being that xmem_pool_alloc() may add extra padding
to the requested size, making the total block size greater than a
page.

Rather than add yet more smarts about TLSF to _xmalloc(), we just
dumbly attempt any request smaller than a page via xmem_pool_alloc()
first, then fall back on xmalloc_whole_pages() if this fails.

Based on bug diagnosis and initial patch by John Byrne <john.l.byrne@hp.com>

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
index 3f85389e237209866b301bdd674ccf55efa52bdd..6be78e1b98d14e9ded22afcdc04aac34cf897d70 100644 (file)
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -553,7 +553,7 @@ static void tlsf_init(void)
 
 void *_xmalloc(unsigned long size, unsigned long align)
 {
-    void *p;
+    void *p = NULL;
     u32 pad;
 
     ASSERT(!in_irq());
@@ -566,10 +566,10 @@ void *_xmalloc(unsigned long size, unsigned long align)
     if ( !xenpool )
         tlsf_init();
 
-    if ( size >= (PAGE_SIZE - (2*BHDR_OVERHEAD)) )
-        p = xmalloc_whole_pages(size);
-    else
+    if ( size < PAGE_SIZE )
         p = xmem_pool_alloc(size, xenpool);
+    if ( p == NULL )
+        p = xmalloc_whole_pages(size);
 
     /* Add alignment padding. */
     if ( (pad = -(long)p & (align - 1)) != 0 )
@@ -603,7 +603,7 @@ void xfree(void *p)
         ASSERT(!(b->size & 1));
     }
 
-    if ( b->size >= (PAGE_SIZE - (2*BHDR_OVERHEAD)) )
+    if ( b->size >= PAGE_SIZE )
         free_xenheap_pages((void *)b, get_order_from_bytes(b->size));
     else
         xmem_pool_free(p, xenpool);