Re: [PATCH] x86: use __GFP_NORETRY in the case of GFP_DMA with pci-nommu

FUJITA Tomonori
2008-09-06T12:19:25Z

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;