[Xen-changelog] [xen-4.0-testing] x86: fix Dom0 booting time regression

["Xen patchbot-4.0-testing" <patchbot-4.0-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1273481208 -3600
# Node ID b3fcd496e064b60e41d6b0ed75bf49b78022315d
# Parent  dcff1f6352bbebe38da8cc3c8f82872f04d6a0a0
x86: fix Dom0 booting time regression

Unfortunately the changes in c/s 21035 caused boot time to go up
significantly on certain large systems. To rectify this without going
back to the old behavior, introduce a new memory allocation flag so
that Dom0 allocations can exhaust non-DMA memory before starting to
consume DMA memory. For the latter, the behavior introduced in
aforementioned c/s gets retained, while for the former we can now even
try larger chunks first.

This builds on the fact that alloc_chunk() gets called with non-
increasing 'max_pages' arguments, end hence it can store locally the
allocation order last used (as larger order allocations can't succeed
during subsequent invocations if they failed once).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
xen-unstable changeset:   21272:b07edd50661e
xen-unstable date:        Tue May 04 12:42:21 2010 +0100
---
 xen/arch/x86/domain_build.c |   36 +++++++++++++++++++++++-------------
 xen/common/page_alloc.c     |    5 +++--
 xen/include/xen/mm.h        |    2 ++
 3 files changed, 28 insertions(+), 15 deletions(-)

diff -r dcff1f6352bb -r b3fcd496e064 xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c       Mon May 10 09:46:25 2010 +0100
+++ b/xen/arch/x86/domain_build.c       Mon May 10 09:46:48 2010 +0100
@@ -125,26 +125,36 @@ static struct page_info * __init alloc_c
 static struct page_info * __init alloc_chunk(
     struct domain *d, unsigned long max_pages)
 {
+    static unsigned int __initdata last_order = MAX_ORDER;
+    static unsigned int __initdata memflags = MEMF_no_dma;
     struct page_info *page;
-    unsigned int order, free_order;
-
-    /*
-     * Allocate up to 2MB at a time: It prevents allocating very large chunks
-     * from DMA pools before the >4GB pool is fully depleted.
-     */
-    if ( max_pages > (2UL << (20 - PAGE_SHIFT)) )
-        max_pages = 2UL << (20 - PAGE_SHIFT);
-    order = get_order_from_pages(max_pages);
-    if ( (max_pages & (max_pages-1)) != 0 )
-        order--;
-    while ( (page = alloc_domheap_pages(d, order, 0)) == NULL )
+    unsigned int order = get_order_from_pages(max_pages), free_order;
+
+    if ( order > last_order )
+        order = last_order;
+    else if ( max_pages & (max_pages - 1) )
+        --order;
+    while ( (page = alloc_domheap_pages(d, order, memflags)) == NULL )
         if ( order-- == 0 )
             break;
+    if ( page )
+        last_order = order;
+    else if ( memflags )
+    {
+        /*
+         * Allocate up to 2MB at a time: It prevents allocating very large
+         * chunks from DMA pools before the >4GB pool is fully depleted.
+         */
+        last_order = 21 - PAGE_SHIFT;
+        memflags = 0;
+        return alloc_chunk(d, max_pages);
+    }
+
     /*
      * Make a reasonable attempt at finding a smaller chunk at a higher
      * address, to avoid allocating from low memory as much as possible.
      */
-    for ( free_order = order; page && order--; )
+    for ( free_order = order; !memflags && page && order--; )
     {
         struct page_info *pg2;
 
diff -r dcff1f6352bb -r b3fcd496e064 xen/common/page_alloc.c
--- a/xen/common/page_alloc.c   Mon May 10 09:46:25 2010 +0100
+++ b/xen/common/page_alloc.c   Mon May 10 09:46:48 2010 +0100
@@ -1157,8 +1157,9 @@ struct page_info *alloc_domheap_pages(
         pg = alloc_heap_pages(dma_zone + 1, zone_hi, node, order, memflags);
 
     if ( (pg == NULL) &&
-         ((pg = alloc_heap_pages(MEMZONE_XEN + 1, zone_hi,
-                                 node, order, memflags)) == NULL) )
+         ((memflags & MEMF_no_dma) ||
+          ((pg = alloc_heap_pages(MEMZONE_XEN + 1, zone_hi,
+                                  node, order, memflags)) == NULL)) )
          return NULL;
 
     if ( (d != NULL) && assign_pages(d, pg, order, memflags) )
diff -r dcff1f6352bb -r b3fcd496e064 xen/include/xen/mm.h
--- a/xen/include/xen/mm.h      Mon May 10 09:46:25 2010 +0100
+++ b/xen/include/xen/mm.h      Mon May 10 09:46:48 2010 +0100
@@ -79,6 +79,8 @@ int assign_pages(
 #define  MEMF_populate_on_demand (1U<<_MEMF_populate_on_demand)
 #define _MEMF_tmem        2
 #define  MEMF_tmem        (1U<<_MEMF_tmem)
+#define _MEMF_no_dma      3
+#define  MEMF_no_dma      (1U<<_MEMF_no_dma)
 #define _MEMF_node        8
 #define  MEMF_node(n)     ((((n)+1)&0xff)<<_MEMF_node)
 #define _MEMF_bits        24

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