Messages in this thread | | | Subject | Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default | From | "Aneesh Kumar K.V" <> | Date | Thu, 28 Feb 2019 18:02:53 +0530 |
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On 2/28/19 3:10 PM, Jan Kara wrote: > On Thu 28-02-19 14:05:22, Aneesh Kumar K.V wrote: >> Add a flag to indicate the ability to do huge page dax mapping. On architecture >> like ppc64, the hypervisor can disable huge page support in the guest. In >> such a case, we should not enable huge page dax mapping. This patch adds >> a flag which the architecture code will update to indicate huge page >> dax mapping support. >> >> Architectures mostly do transparent_hugepage_flag = 0; if they can't >> do hugepages. That also takes care of disabling dax hugepage mapping >> with this change. >> >> Without this patch we get the below error with kvm on ppc64. >> >> [ 118.849975] lpar: Failed hash pte insert with error -4 >> >> NOTE: The patch also use >> >> echo never > /sys/kernel/mm/transparent_hugepage/enabled >> to disable dax huge page mapping. >> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > > Added Dan to CC for opinion. I kind of fail to see why you don't use > TRANSPARENT_HUGEPAGE_FLAG for this. I know that technically DAX huge pages > and normal THPs are different things but so far we've tried to avoid making > that distinction visible to userspace.
I would also like to use the same flag. Was not sure whether it was ok. In fact that is one of the reason I hooked this to /sys/kernel/mm/transparent_hugepage/enabled. If we are ok with using same flag, we can kill the vma_is_dax() check completely.
-aneesh
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