Re: [PATCH 6/6] io_uring: cache nodes and mapped buffers

[Keith Busch <kbusch@kernel.org>]

On Fri, Feb 07, 2025 at 12:41:17PM +0000, Pavel Begunkov wrote:
> On 2/3/25 15:45, Keith Busch wrote:
> > +struct io_alloc_cache {
> > +	void			**entries;
> > +	unsigned int		nr_cached;
> > +	unsigned int		max_cached;
> > +	size_t			elem_size;
> > +};
> > +
> >   struct io_buf_table {
> >   	struct io_rsrc_data	data;
> > +	struct io_alloc_cache	node_cache;
> > +	struct io_alloc_cache	imu_cache;
> 
> We can avoid all churn if you kill patch 5/6 and place put the
> caches directly into struct io_ring_ctx. It's a bit better for
> future cache improvements and we can even reuse the node cache
> for files.

I had this that way in an earlier version. The cache is tightly
connected to the buf table, though, so splitting them up makes for some
awkward cleanup. Grouping them together makes it clear their lifetimes
are as a single unit.

The filetable could have moved its bitmap into io_ring_ctx too, but it's
in its own structure like this, and it conceptually makes sense. This is
following in that same pattern.