Jan Beulich
2009-Aug-28 08:14 UTC
[Xen-devel] [PATCH] adjust non-default sized console ring allocation
Using xmalloc() for objects that are guaranteed to be at least as
large as a page is wasteful, as it will always result in more (here:
double the amount) being allocated.
The other adjustments are more cosmetic:
- Updating conring and conring_size can be done so NMI/MCE generated
messages don''t use the new (larger) size with the old (smaller)
buffer.
- The size printed can be in KiB (for the value to be easier to grasp)
since it is always a multiple of the default of 16KiB.
One remaining problem I see is that the allocation happens after all
CPUs got brought up: With that process (plus the prior ACPI table
parsing) being what generates (on large systems) by far the largest
amount of messages, one of the primary uses of that option - getting at
all boot messages - seems to be out of reach at present. Prior to
discovering this boot option exists at all (it didn''t in 3.3) I was
about to implement a solution where the ring would sit at the end of
.bss, and thus be sizeable at very early boot time; maybe that''s still
worth considering as an alternative to the current approach?
Signed-off-by: Jan Beulich <jbeulich@novell.com>
--- 2009-08-18.orig/xen/drivers/char/console.c 2009-08-24 17:51:39.000000000
+0200
+++ 2009-08-18/xen/drivers/char/console.c 2009-08-26 16:47:56.000000000 +0200
@@ -608,7 +608,7 @@ void __init console_init_postirq(void)
if ( opt_conring_size < conring_size )
return;
- ring = xmalloc_bytes(opt_conring_size);
+ ring = alloc_xenheap_pages(get_order_from_bytes(opt_conring_size), 0);
if ( ring == NULL )
{
printk("Unable to allocate console ring of %u bytes.\n",
@@ -619,11 +619,12 @@ void __init console_init_postirq(void)
spin_lock_irq(&console_lock);
for ( i = conringc ; i != conringp; i++ )
ring[i & (opt_conring_size - 1)] = conring[i & (conring_size -
1)];
- conring_size = opt_conring_size;
conring = ring;
+ wmb();
+ conring_size = opt_conring_size;
spin_unlock_irq(&console_lock);
- printk("Allocated console ring of %u bytes.\n",
opt_conring_size);
+ printk("Allocated console ring of %u KiB.\n", opt_conring_size
>> 10);
}
void __init console_endboot(void)
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