Hi On Mon, Mar 23, 2015 at 12:57 PM, Tomasz Figa <tf...@chromium.org> wrote: > IOMMU should be able to use single pages as well as bigger blocks, so if > higher order allocations fail, we should not affect state of the system, > with events such as OOM killer, but rather fall back to order 0 > allocations. > > This patch changes the behavior of ARM IOMMU DMA allocator to use > __GFP_NORETRY, which bypasses OOM invocation, for orders higher than > zero and, only if that fails, fall back to normal order 0 allocation > which might invoke OOM killer.
Logical thing to do in IOMMU case :) > > Signed-off-by: Tomasz Figa <tf...@chromium.org> > --- > arch/arm/mm/dma-mapping.c | 27 +++++++++++++++++++++------ > 1 file changed, 21 insertions(+), 6 deletions(-) > > Changes since v1: > (https://patchwork.kernel.org/patch/6015921/) > - do not clear __GFP_NORETRY, as it might come from the caller, > - s/positive order/order higher than 0/. > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 83cd5ac..3f1ac51 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -1150,13 +1150,28 @@ static struct page **__iommu_alloc_buffer(struct > device *dev, size_t size, > gfp |= __GFP_NOWARN | __GFP_HIGHMEM; > > while (count) { > - int j, order = __fls(count); > + int j, order; > + > + for (order = __fls(count); order > 0; --order) { > + /* > + * We do not want OOM killer to be invoked as long > + * as we can fall back to single pages, so we force > + * __GFP_NORETRY for orders higher than zero. > + */ > + pages[i] = alloc_pages(gfp | __GFP_NORETRY, order); > + if (pages[i]) > + break; > + } > > - pages[i] = alloc_pages(gfp, order); > - while (!pages[i] && order) > - pages[i] = alloc_pages(gfp, --order); > - if (!pages[i]) > - goto error; > + if (!pages[i]) { > + /* > + * Fall back to single page allocation. > + * Might invoke OOM killer as last resort. > + */ > + pages[i] = alloc_pages(gfp, 0); I think down the code in this while loop, i & count is being calculated based on the "order" of allocation in the current iteration. Since value of order will be automatically 0 here if (!pages[i]) is true then, why hard code order to value of 0 here. Comment clearly says what this code is doing right? I know it is just a minor thing. Don't know if it is relevant. > + if (!pages[i]) > + goto error; > + } > > if (order) { > split_page(pages[i], order); > -- > 2.2.0.rc0.207.ga3a616c > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-ker...@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel Thanks Ritesh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
