From: Andi Kleen <ak@suse.de>
To: Jens Axboe <axboe@suse.de>
Subject: Re: adding swap workarounds oom - was: Re: Out of Memory: Killed process 16498 (java).
Date: Wed, 1 Mar 2006 15:05:21 +0100
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Cc: Andy Chittenden <AChittenden@bluearc.com>,
       Anton Altaparmakov <aia21@cam.ac.uk>, Andrew Morton <akpm@osdl.org>,
       davej@redhat.com, linux-kernel@vger.kernel.org, lwoodman@redhat.com,
       Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
References: <89E85E0168AD994693B574C80EDB9C270393C104@uk-email.terastack.bluearc.com> <20060301134123.GU4816@suse.de>
In-Reply-To: <20060301134123.GU4816@suse.de>
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On Wednesday 01 March 2006 14:41, Jens Axboe wrote:
> On Wed, Mar 01 2006, Andy Chittenden wrote:
> > with revised patch that does:
> > 
> >                 printk("sg%d: dma=%llx, dma_len=%u/%u, pfn=%lu\n", i,
> > (unsigned long long) sg->dma_address, sg->dma_length, sg->offset,
> > page_to_pfn(sg->page));
> 
> That is correct, thanks!
> 
> > hda: DMA table too small
> > ide dma table, 255 entries, bounce pfn 1310720
> > sg0: dma=81c8800, dma_len=4096/0, pfn=1296369
> 
> Still the same badness here, it's 2kb into a page so straddles two pages
> for one entry.

That's normal if it was in the IOMMU and a merged entry. 

You can try iommu=nomerge.

Or maybe the higher layers are passing in physically continuous pages
that get merged? Not too unlikely at boot.


> 
> Andi, any idea what is going on here? Why is this throwing up all of a
> sudden??

What is throwing up exactly?

There was a change recently in the merging algorithm, but it shouldn't
cause any bad side effects for correct users of *_map_sg()

-Andi

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