Messages in this thread | | | Date | Mon, 11 Apr 2022 21:18:19 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH v2 bpf 1/3] vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP |
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On Mon, Apr 11, 2022 at 04:35:46PM -0700, Song Liu wrote: > Huge page backed vmalloc memory could benefit performance in many cases. > Since some users of vmalloc may not be ready to handle huge pages, > VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge > pages. However, it is not easy to add VM_NO_HUGE_VMAP to all the users > that may try to allocate >= PMD_SIZE pages, but are not ready to handle > huge pages properly.
This is a good place to document what the problems are, and how they are hard to track down (e.g. because the allocations are passed down I/O stacks)
> > Replace VM_NO_HUGE_VMAP with an opt-in flag, VM_ALLOW_HUGE_VMAP, so that > users that benefit from huge pages could ask specificially. > > Also, replace vmalloc_no_huge() with opt-in helper vmalloc_huge().
We still need to find out what the primary users of the large vmalloc hashes was and convert them.
> +extern void *vmalloc_huge(unsigned long size) __alloc_size(1);
No need for the extern.
> +EXPORT_SYMBOL(vmalloc_huge);
EXPORT_SYMBOL_GPL for all advanced vmalloc functionality, please.
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