On 18 Feb 2021, at 12:25, Jason Gunthorpe wrote: > On Thu, Feb 18, 2021 at 02:45:54PM +0000, Matthew Wilcox wrote: >> On Wed, Feb 17, 2021 at 11:02:52AM -0800, Andrew Morton wrote: >>> On Wed, 17 Feb 2021 10:49:25 -0800 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote: >>>> page structs are not guaranteed to be contiguous for gigantic pages. The >>> >>> June 2014. That's a long lurk time for a bug. I wonder if some later >>> commit revealed it. >> >> I would suggest that gigantic pages have not seen much use. Certainly >> performance with Intel CPUs on benchmarks that I've been involved with >> showed lower performance with 1GB pages than with 2MB pages until quite >> recently. > > I suggested in another thread that maybe it is time to consider > dropping this "feature" You mean dropping gigantic page support in hugetlb? > > If it has been slightly broken for 7 years it seems a good bet it > isn't actually being used. > > The cost to fix GUP to be compatible with this will hurt normal > GUP performance - and again, that nobody has hit this bug in GUP > further suggests the feature isn't used.. A easy fix might be to make gigantic hugetlb page depends on CONFIG_SPARSEMEM_VMEMMAP, which guarantee all struct pages are contiguous. — Best Regards, Yan Zi
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