From db9f600b96c16bb3c7f094e294fbdd370226ad86 Mon Sep 17 00:00:00 2001 From: Miquel van Smoorenburg Date: Wed, 28 May 2008 10:31:25 +0200 Subject: x86: pci-dma.c: use __GFP_NO_OOM instead of __GFP_NORETRY On Wed, 2008-05-28 at 04:47 +0200, Andi Kleen wrote: > > So... why not just remove the setting of __GFP_NORETRY? Why is it > > wrong to oom-kill things in this case? > > When the 16MB zone overflows (which can be common in some workloads) > calling the OOM killer is pretty useless because it has barely any > real user data [only exception would be the "only 16MB" case Alan > mentioned]. Killing random processes in this case is bad. > > I think for 16MB __GFP_NORETRY is ok because there should be > nothing freeable in there so looping is useless. Only exception would be the > "only 16MB total" case again but I'm not sure 2.6 supports that at all > on x86. > > On the other hand d_a_c() does more allocations than just 16MB, especially > on 64bit and the other zones need different strategies. Okay, so how about this then ? Signed-off-by: Ingo Molnar --- arch/x86/kernel/pci-dma.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'arch/x86/kernel/pci-dma.c') diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index c5ef1af8e79d..069e843f0b93 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -397,9 +397,6 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, if (dev->dma_mask == NULL) return NULL; - /* Don't invoke OOM killer */ - gfp |= __GFP_NORETRY; - #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 @@ -410,7 +407,9 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, #endif again: - page = dma_alloc_pages(dev, gfp, get_order(size)); + /* Don't invoke OOM killer or retry in lower 16MB DMA zone */ + page = dma_alloc_pages(dev, + (gfp & GFP_DMA) ? gfp | __GFP_NORETRY : gfp, get_order(size)); if (page == NULL) return NULL; -- cgit v1.2.2 From b7f09ae583c49d28b2796d2fa5893dcf822e3a10 Mon Sep 17 00:00:00 2001 From: Miquel van Smoorenburg Date: Thu, 5 Jun 2008 18:14:44 +0200 Subject: 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. [ mingo@elte.hu: converted to delta patch ontop of previous version. ] Signed-off-by: Miquel van Smoorenburg Signed-off-by: Ingo Molnar --- arch/x86/kernel/pci-dma.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'arch/x86/kernel/pci-dma.c') diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 069e843f0b93..dc00a1331ace 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -378,6 +378,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, 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); @@ -397,19 +398,25 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, if (dev->dma_mask == NULL) return NULL; + /* 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: - /* Don't invoke OOM killer or retry in lower 16MB DMA zone */ page = dma_alloc_pages(dev, - (gfp & GFP_DMA) ? gfp | __GFP_NORETRY : gfp, get_order(size)); + noretry ? gfp | __GFP_NORETRY : gfp, get_order(size)); if (page == NULL) return NULL; -- cgit v1.2.2