Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB

Vito Caputo
2021-11-16T19:46:46Z

On Tue, Nov 16, 2021 at 08:25:33PM +0100, Drew DeVault wrote:
> On Tue Nov 16, 2021 at 8:21 PM CET, Vito Caputo wrote:
> > Considering a single fullscreen 32bpp 4K-resolution framebuffer is
> > ~32MiB, I'm not convinced this is really correct in nearly 2022.
>
> Can you name a practical use-case where you'll be doing I/O with
> uncompressed 4K framebuffers? The kind of I/O which is supported by
> io_uring, to be specific, not, say, handing it off to libdrm.

Obviously video/image editing software tends to operate on raw frames,
and sometimes even persists them via filesystems.

I haven't given it a lot of thought, but a framebuffer is a commonly
used unit of memory allocation in code run on the CPU I've written
over the years. Being able to pin those for something like io_uring
(or some other DMA-possible interface) seems like an obvious
memory-hungry thing to consider here if we're talking default upper
bounds.

Regards,
Vito Caputo