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SubjectRe: [PATCH] x86: use __GFP_NORETRY in the case of GFP_DMA with pci-nommu
On Sat, Sep 06, 2008 at 09:18:37PM +0900, FUJITA Tomonori wrote:
> On Fri, 5 Sep 2008 12:43:05 +0200
> Joerg Roedel <joerg.roedel@amd.com> wrote:
>
> > On Fri, Sep 05, 2008 at 05:58:48PM +0900, FUJITA Tomonori wrote:
> > > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > > ---
> > > arch/x86/kernel/pci-nommu.c | 3 +++
> > > 1 files changed, 3 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
> > > index 526b2db..3495f88 100644
> > > --- a/arch/x86/kernel/pci-nommu.c
> > > +++ b/arch/x86/kernel/pci-nommu.c
> > > @@ -102,6 +102,9 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
> > > if (dma_mask == DMA_24BIT_MASK)
> > > gfp |= GFP_DMA;
> > > again:
> > > + if (gfp & GFP_DMA)
> > > + gfp |= __GFP_NORETRY;
> > > +
> >
> > Huh? Why that? The __GFP_NORETRY is a hint from the caller to the page
> > allocator on how aggressive it should try to allocate memory. I don't
> > think the DMA code should touch those flags unless there is a very very
> > good reason for it.
>
> The current comment is reasonable for me:
>
> /* Don't invoke OOM killer or retry in lower 16MB DMA zone */
> if (gfp & __GFP_DMA)
> noretry = 1;

Ok, so please add a comment to this so we know in the future why this is
there.

Joerg

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