[gPXE] [PATCH] Merge adjacent memory regions of same type

[Silver, Geoffrey]

I'd like to state for the record that this patch resolves a specific gPXE issue on some HP BL685c G1 servers where a large boot image (eg. ESXi 4.1) runs through the available memory in the first region.  It would be great if this patch would make it into gPXE 1.0.2.

--
Geoffrey Silver
Global Infrastructure
CITADEL


-----Original Message-----
From: gpxe-bounces at etherboot.org [mailto:gpxe-bounces at etherboot.org] On Behalf Of Casey Dahlin
Sent: Tuesday, October 12, 2010 3:37 PM
To: gpxe at etherboot.org
Cc: jeder at redhat.com; gcosta at redhat.com
Subject: [gPXE] [PATCH] Merge adjacent memory regions of same type

Some BIOSes can report multiple memory regions which may be adjacent and the same type. Since only the first region is used in the mboot.c32 layer it's possible to run out of memory when loading all of the boot modules. One may get around this problem by having gPXE merge these memory regions internally.

--- a/src/arch/i386/firmware/pcbios/memmap.c   2009-10-21 14:05:47.000000000 -0500
+++ b/src/arch/i386/firmware/pcbios/memmap.c   2010-08-27 17:27:45.000000000 -0500
@@ -156,6 +156,7 @@
  */
 static int meme820 ( struct memory_map *memmap ) {
        struct memory_region *region = memmap->regions;
+  struct memory_region *prev_region = NULL;
        uint32_t next = 0;
        uint32_t smap;
        size_t size;
@@ -238,9 +239,16 @@

                region->start = e820buf.start;
                region->end = e820buf.start + e820buf.len;
-               region++;
-               memmap->count++;
-
+    /* Check for adjacent regions and merge them. */
+    if (prev_region && region->start == prev_region->end) {
+        prev_region->end = region->end;
+    }
+    else {
+        prev_region = region;
+        region++;
+        memmap->count++;
+    }
+
                if ( memmap->count >= ( sizeof ( memmap->regions ) /
                                        sizeof ( memmap->regions[0] ) ) ) {
                        DBG ( "INT 15,e820 too many regions returned\n" );

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