Re: [PATCH v2 0/4] io_uring/rsrc: coalescing multi-hugepage registered buffers

[Jens Axboe <axboe@kernel.dk>]

On 5/10/24 11:52 PM, Chenliang Li wrote:
> Registered buffers are stored and processed in the form of bvec array,
> each bvec element typically points to a PAGE_SIZE page but can also work
> with hugepages. Specifically, a buffer consisting of a hugepage is
> coalesced to use only one hugepage bvec entry during registration.
> This coalescing feature helps to save both the space and DMA-mapping time.
> 
> However, currently the coalescing feature doesn't work for multi-hugepage
> buffers. For a buffer with several 2M hugepages, we still split it into
> thousands of 4K page bvec entries while in fact, we can just use a
> handful of hugepage bvecs.
> 
> This patch series enables coalescing registered buffers with more than
> one hugepages. It optimizes the DMA-mapping time and saves memory for
> these kind of buffers.

This series looks much better. Do you have a stand-alone test case
for this? We should have that in liburing. Then we can also augment it
with edge cases to ensure this is all safe and sound.

-- 
Jens Axboe