On Wed, Nov 21, 2018 at 04:47:48PM +0000, John Garry wrote: > On 21/11/2018 16:07, Will Deacon wrote: > >On Wed, Nov 21, 2018 at 10:54:10PM +0800, John Garry wrote: > >>From: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> > >> > >>Change function __iommu_dma_alloc_pages() to allocate pages for DMA from > >>respective device NUMA node. The ternary operator which would be for > >>alloc_pages_node() is tidied along with this. > >> > >>We also include a change to use kvzalloc() for kzalloc()/vzalloc() > >>combination. > >> > >>Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> > >>[JPG: Added kvzalloc(), drop pages ** being device local, tidied ternary > >>operator] > >>Signed-off-by: John Garry <john.ga...@huawei.com> > > > >Weird, you're missing a diffstat here. > > > >Anyway, the patch looks fine to me, but it would be nice if you could > >justify the change with some numbers. Do you actually see an improvement > >from this change? > > > > Hi Will, > > Ah, I missed adding my comments explaining the motivation. It would be > better in the commit log. Anyway, here's the snippet: > > " ... as mentioned in [3], dma_alloc_coherent() uses the locality > information from the device - as in direct DMA - so this patch is just > applying this same policy. > > [3] > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1692998.html"
Yes, please add to this to the commit log. > I did have some numbers to show improvement in some scenarios when I tested > this a while back which I'll dig out. > > However I would say that some scenarios will improve and the opposite for > others with this change, considering different conditions in which DMA > memory may be used. Well, if you can show that it's useful in some cases and not catastrophic in others, then I think shooting for parity with direct DMA is a reasonable justification for the change. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu