Re: [Xen-devel] Bootup regression introduced by 7bd0b0f0da3b1ec11cbcc798eb0ef747a1184077 ("memblock: Reimplement memblock allocation using reverse free area iterato") in v3.3-rc0

[Tejun Heo <tj@xxxxxxxxxx>]

On Tue, Jan 10, 2012 at 03:28:38PM -0500, Konrad Rzeszutek Wilk wrote:
> With that patch I get this when trying to launch a 4GB xen guest:
> 
> kernel="/mnt/lab/latest/vmlinuz"
> ramdisk="/mnt/lab/latest/initramfs.cpio.gz"
> extra="console=hvc0 debug earlyprintk=xen" 
> memory=4096
> maxmem=8192
> vcpus=4
> on_crash="preserve"
> vif = [ 'mac=00:0F:4B:00:00:68, bridge=switch' ]
> vfb = [ 'vnc=1, vnclisten=0.0.0.0,vncunused=1'
> 
> If I change the "memory" to be "4000" it or if I revert the
> mention git commit it boots. This is what I get with the mentioned
> git commit:

Heh, interesting.  Can you please apply the following patch and report
the failing boot log?

Thanks.

diff --git a/mm/memblock.c b/mm/memblock.c
index 2f55f19..978b58eff 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -102,6 +102,10 @@ phys_addr_t __init_memblock 
memblock_find_in_range_node(phys_addr_t start,
        /* align @size to avoid excessive fragmentation on reserved array */
        size = round_up(size, align);
 
+       printk("memblock_find: [0x%llx, 0x%llx) size=%llu align=%llu nid=%d\n",
+              (unsigned long long)start, (unsigned long long)end,
+              (unsigned long long)size, (unsigned long long)align, nid);
+
        /* pump up @end */
        if (end == MEMBLOCK_ALLOC_ACCESSIBLE)
                end = memblock.current_limit;
@@ -110,13 +114,27 @@ phys_addr_t __init_memblock 
memblock_find_in_range_node(phys_addr_t start,
        start = max3(start, size, (phys_addr_t)PAGE_SIZE);
        end = max(start, end);
 
+       printk("memblock_find: [0x%llx, 0x%llx) - adjusted\n",
+              (unsigned long long)start, (unsigned long long)end);
+
        for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) {
+               printk("memblock_find: cand [0x%llx, 0x%llx) -> ",
+                      (unsigned long long)this_start,
+                      (unsigned long long)this_end);
+
                this_start = clamp(this_start, start, end);
                this_end = clamp(this_end, start, end);
 
+               printk("[0x%llx, 0x%llx) ",
+                      (unsigned long long)this_start,
+                      (unsigned long long)this_end);
+
                cand = round_down(this_end - size, align);
-               if (cand >= this_start)
+               if (cand >= this_start) {
+                       printk("- success %llx\n", (unsigned long long)cand);
                        return cand;
+               }
+               printk("- rejected\n");
        }
        return 0;
 }

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