[lkml]   [2019]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default
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 <>
> 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.


 \ /
  Last update: 2019-02-28 13:34    [W:0.163 / U:7.176 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site