Re: [PATCH] io_uring: Use slab for struct io_buffer objects

[Gabriel Krisman Bertazi <krisman@suse.de>]

Gabriel Krisman Bertazi <krisman@suse.de> writes:

> The allocation of struct io_buffer for metadata of provided buffers is
> done through a custom allocator that directly gets pages and
> fragments them.  But, slab would do just fine, as this is not a hot path
> (in fact, it is a deprecated feature) and, by keeping a custom allocator
> implementation we lose benefits like tracking, poisoning,
> sanitizers. Finally, the custom code is more complex and requires
> keeping the list of pages in struct ctx for no good reason.  This patch
> cleans this path up and just uses slab.
>
> I microbenchmarked it by forcing the allocation of a large number of
> objects with the least number of io_uring commands possible (keeping
> nbufs=USHRT_MAX), with and without the patch.  There is a slight
> increase in time spent in the allocation with slab, of course, but even
> when allocating to system resources exhaustion, which is not very
> realistic and happened around 1/2 billion provided buffers for me, it
> wasn't a significant hit in system time.  Specially if we think of a
> real-world scenario, an application doing register/unregister of
> provided buffers will hit ctx->io_buffers_cache more often than actually
> going to slab.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>

Hi Jens,

Any feedback on this?

-- 
Gabriel Krisman Bertazi