Messages in this thread | | | Date | Wed, 12 Apr 2023 13:13:02 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v2] mm: hugetlb_vmemmap: provide stronger vmemmap allocation guarantees |
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Lots of questions (ie, missing information!)
On Wed, 12 Apr 2023 19:59:39 +0000 Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> HugeTLB pages have a struct page optimizations where struct pages for tail > pages are freed. However, when HugeTLB pages are destroyed, the memory for > struct pages (vmemmap) need to be allocated again. > > Currently, __GFP_NORETRY flag is used to allocate the memory for vmemmap, > but given that this flag makes very little effort to actually reclaim > memory the returning of huge pages back to the system can be problem.
Are there any reports of this happening in the real world?
> Lets > use __GFP_RETRY_MAYFAIL instead. This flag is also performs graceful > reclaim without causing ooms, but at least it may perform a few retries, > and will fail only when there is genuinely little amount of unused memory > in the system.
If so, does this change help?
If the allocation attempt fails, what are the consequences?
What are the potential downsides to this change? Why did we choose __GFP_NORETRY in the first place?
What happens if we try harder (eg, GFP_KERNEL)?
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