Messages in this thread | | | Date | Tue, 10 Jun 2008 12:23:47 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] 2.6.26-rc: x86: pci-dma.c: use __GFP_NO_OOM instead of __GFP_NORETRY |
| |
* Miquel van Smoorenburg <mikevs@xs4all.net> wrote:
> On Mon, 2008-06-02 at 12:15 +0200, Ingo Molnar wrote: > > * Miquel van Smoorenburg <mikevs@xs4all.net> wrote: > > > > > Okay, so how about this then ? > > > > > > applied to tip/pci-for-jesse for more testing. Thanks, > > I've thought about it a bit more, and I think the actual patch that > really does what everybody wants is this one instead:
applied a delta patch version of the one below to tip/pci-for-jesse. Thanks,
Ingo
> [PATCH] x86: pci-dma.c: don't always add __GFP_NORETRY to gfp > > Currently arch/x86/kernel/pci-dma.c always adds __GFP_NORETRY > to the allocation flags, because it wants to be reasonably > sure not to deadlock when calling alloc_pages(). > > But really that should only be done in two cases: > - when allocating memory in the lower 16 MB DMA zone. > If there's no free memory there, waiting or OOM killing is of no use > - when optimistically trying an allocation in the DMA32 zone > when dma_mask < DMA_32BIT_MASK hoping that the allocation > happens to fall within the limits of the dma_mask > > Also blindly adding __GFP_NORETRY to the the gfp variable might > not be a good idea since we then also use it when calling > dma_ops->alloc_coherent(). Clearing it might also not be a > good idea, dma_alloc_coherent()'s caller might have set it > on purpose. The gfp variable should not be clobbered. > > Signed-off-by: Miquel van Smoorenburg <miquels@cistron.nl> > > --- linux-2.6.26-rc4.orig/arch/x86/kernel/pci-dma.c 2008-05-26 20:08:11.000000000 +0200 > +++ linux-2.6.26-rc4/arch/x86/kernel/pci-dma.c 2008-06-05 17:51:41.000000000 +0200 > @@ -378,6 +378,7 @@ dma_alloc_coherent(struct device *dev, s > struct page *page; > unsigned long dma_mask = 0; > dma_addr_t bus; > + int noretry = 0; > > /* ignore region specifiers */ > gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32); > @@ -397,20 +398,25 @@ dma_alloc_coherent(struct device *dev, s > if (dev->dma_mask == NULL) > return NULL; > > - /* Don't invoke OOM killer */ > - gfp |= __GFP_NORETRY; > + /* Don't invoke OOM killer or retry in lower 16MB DMA zone */ > + if (gfp & __GFP_DMA) > + noretry = 1; > > #ifdef CONFIG_X86_64 > /* Why <=? Even when the mask is smaller than 4GB it is often > larger than 16MB and in this case we have a chance of > finding fitting memory in the next higher zone first. If > not retry with true GFP_DMA. -AK */ > - if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA)) > + if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA)) { > gfp |= GFP_DMA32; > + if (dma_mask < DMA_32BIT_MASK) > + noretry = 1; > + } > #endif > > again: > - page = dma_alloc_pages(dev, gfp, get_order(size)); > + page = dma_alloc_pages(dev, > + noretry ? gfp | __GFP_NORETRY : gfp, get_order(size)); > if (page == NULL) > return NULL; > >
| |