Messages in this thread | | | From | "Song Bao Hua (Barry Song)" <> | Subject | RE: [PATCH v3 1/2] dma-direct: provide the ability to reserve per-numa CMA | Date | Wed, 22 Jul 2020 21:41:50 +0000 |
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> -----Original Message----- > From: Christoph Hellwig [mailto:hch@lst.de] > Sent: Thursday, July 23, 2020 2:30 AM > To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com> > Cc: hch@lst.de; m.szyprowski@samsung.com; robin.murphy@arm.com; > will@kernel.org; ganapatrao.kulkarni@cavium.com; > catalin.marinas@arm.com; iommu@lists.linux-foundation.org; Linuxarm > <linuxarm@huawei.com>; linux-arm-kernel@lists.infradead.org; > linux-kernel@vger.kernel.org; Jonathan Cameron > <jonathan.cameron@huawei.com>; Nicolas Saenz Julienne > <nsaenzjulienne@suse.de>; Steve Capper <steve.capper@arm.com>; Andrew > Morton <akpm@linux-foundation.org>; Mike Rapoport <rppt@linux.ibm.com> > Subject: Re: [PATCH v3 1/2] dma-direct: provide the ability to reserve > per-numa CMA > +cc Prime and Daode who are interested in this patchset.
> On Sun, Jun 28, 2020 at 11:12:50PM +1200, Barry Song wrote: > > struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t > gfp) > > { > > size_t count = size >> PAGE_SHIFT; > > struct page *page = NULL; > > struct cma *cma = NULL; > > + int nid = dev ? dev_to_node(dev) : NUMA_NO_NODE; > > + bool alloc_from_pernuma = false; > > + > > + if ((count <= 1) && !(dev && dev->cma_area)) > > + return NULL; > > > > if (dev && dev->cma_area) > > cma = dev->cma_area; > > - else if (count > 1) > > + else if ((nid != NUMA_NO_NODE) && > dma_contiguous_pernuma_area[nid] > > + && !(gfp & (GFP_DMA | GFP_DMA32))) { > > + cma = dma_contiguous_pernuma_area[nid]; > > + alloc_from_pernuma = true; > > + } else { > > cma = dma_contiguous_default_area; > > + } > > I find the function rather confusing now. What about something > like (this relies on the fact that dev should never be NULL in the > DMA API) > > struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) > { > size_t cma_align = min_t(size_t, get_order(size), > CONFIG_CMA_ALIGNMENT); > size_t count = size >> PAGE_SHIFT; > > if (gfpflags_allow_blocking(gfp)) > return NULL; > gfp &= __GFP_NOWARN; > > if (dev->cma_area)
I got a kernel robot warning which said dev should be checked before being accessed when I did a similar change in v1. Probably it was an invalid warning if dev should never be null.
> return cma_alloc(dev->cma_area, count, cma_align, gfp); > if (count <= 1) > return NULL; > > if (IS_ENABLED(CONFIG_PERNODE_CMA) && !(gfp & (GFP_DMA | > GFP_DMA32)) { > int nid = dev_to_node(dev); > struct cma *cma = dma_contiguous_pernuma_area[nid]; > struct page *page; > > if (cma) { > page = cma_alloc(cma, count, cma_align, gfp); > if (page) > return page; > } > } > > return cma_alloc(dma_contiguous_default_area, count, cma_align, gfp); > }
Yes, it looks much better.
> > > + /* > > + * otherwise, page is from either per-numa cma or default cma > > + */ > > + int nid = page_to_nid(page); > > + > > + if (nid != NUMA_NO_NODE) { > > + if (cma_release(dma_contiguous_pernuma_area[nid], page, > > + PAGE_ALIGN(size) >> PAGE_SHIFT)) > > + return; > > + } > > + > > + if (cma_release(dma_contiguous_default_area, page, > > How can page_to_nid ever return NUMA_NO_NODE?
I thought page_to_nid would return NUMA_NO_NODE if CONFIG_NUMA is not enabled. Probably I was wrong. Will get it fixed in v4.
Thanks Barry
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