Re: Kernel panic when compiling with SMP support

From: Chuck Ebbert
Date: Sat Feb 25 2006 - 01:42:55 EST


In-Reply-To: <1140732949.5733.13.camel@xxxxxxxxxxxxxxxxxxxxxx>

On Thu, 23 Feb 2006 at 14:15:49 -0800, Chris Largret wrote:

> While tinkering with this the last couple days, I've started to notice
> that the infamous OOM killer is running loose when I enable SMP. dmesg
> is filled with messages like this (this is from the boot-up scripts and
> I should have more than enough memory):
>
>
> oom-killer: gfp_mask=0xd1, order=3
>
> Call Trace: <ffffffff8104ed46>{out_of_memory+58}
> <ffffffff8104ff30>{__alloc_pages+534}
> <ffffffff8104ffee>{__get_free_pages+48} <ffffffff8117d8e9>{dma_mem_alloc+31}
> <ffffffff81183e70>{floppy_open+348} <ffffffff81072125>{do_open+172}
> <ffffffff810724b4>{blkdev_open+0} <ffffffff810724dc>{blkdev_open

It wants 32K of contiguous DMA memory. You have 44K free but it's probably
not contiguous.

Maybe this patch from Jens Axboe would help?

=============================================================================

Can you give this a shot? Untested, as I cannot reproduce it here.

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 41387f5..a6cfe7d 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -631,21 +631,15 @@ static inline int ordered_bio_endio(stru
**/
void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
{
- unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
+ q->bounce_gfp = GFP_NOIO;

- /*
- * set appropriate bounce gfp mask -- unfortunately we don't have a
- * full 4GB zone, so we have to resort to low memory for any bounces.
- * ISA has its own < 16MB zone.
- */
- if (bounce_pfn < blk_max_low_pfn) {
- BUG_ON(dma_addr < BLK_BOUNCE_ISA);
+ if (dma_addr < ISA_DMA_THRESHOLD) {
init_emergency_isa_pool();
- q->bounce_gfp = GFP_NOIO | GFP_DMA;
- } else
- q->bounce_gfp = GFP_NOIO;
+ q->bounce_gfp |= GFP_DMA;
+ } else if (dma_addr < DMA_32BIT_MASK)
+ q->bounce_gfp |= GFP_DMA32;

- q->bounce_pfn = bounce_pfn;
+ q->bounce_pfn = dma_addr >> PAGE_SHIFT;
}

EXPORT_SYMBOL(blk_queue_bounce_limit);
--
Chuck
"Equations are the Devil's sentences." --Stephen Colbert
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