Messages in this thread | | | From | Florian Weimer <> | Subject | Re: [PATCH 2/2] mm: mmap: map MAP_STACK to VM_NOHUGEPAGE | Date | Wed, 31 Jan 2024 08:53:40 +0100 |
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* Yang Shi:
> From: Yang Shi <yang@os.amperecomputing.com> > > The commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP > boundaries") incured regression for stress-ng pthread benchmark [1]. > It is because THP get allocated to pthread's stack area much more possible > than before. Pthread's stack area is allocated by mmap without VM_GROWSDOWN > or VM_GROWSUP flag, so kernel can't tell whether it is a stack area or not. > > The MAP_STACK flag is used to mark the stack area, but it is a no-op on > Linux. Mapping MAP_STACK to VM_NOHUGEPAGE to prevent from allocating > THP for such stack area.
Doesn't this introduce a regression in the other direction, where workloads expect to use a hugepage TLB entry for the stack?
It's seems an odd approach to fixing the stress-ng regression. Isn't it very much coding to the benchmark?
Thanks, Florian
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