Re: [PATCHv4 5/5] io_uring: cache nodes and mapped buffers

[Keith Busch <kbusch@kernel.org>]

On Thu, Feb 20, 2025 at 04:06:21PM +0000, Pavel Begunkov wrote:
> On 2/20/25 15:24, Keith Busch wrote:
> > > > +		node = io_cache_alloc(&ctx->buf_table.node_cache, GFP_KERNEL);
> > > 
> > > That's why node allocators shouldn't be a part of the buffer table.
> > 
> > Are you saying you want file nodes to also subscribe to the cache? The
> 
> Yes, but it might be easier for you to focus on finalising the essential
> parts, and then we can improve later.
> 
> > two tables can be resized independently of each other, we don't know how
> > many elements the cache needs to hold.
> 
> I wouldn't try to correlate table sizes with desired cache sizes,
> users can have quite different patterns like allocating a barely used
> huge table. And you care about the speed of node change, which at
> extremes is rather limited by CPU and performance and not spatiality
> of the table. And you can also reallocate it as well.

Having the cache size and lifetime match a table that it's providing
seems as simple as I can make this. This is still an optimization at the
end of the day, so it's not strictly necessary to take the last two
patches from this series to make zero copy work if you don't want to
include it from the beginning.