netdev - Re: [PATCH net-next v1 1/2] rust: add delay abstraction

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Message-ID: <CAH5fLgj1y=h38pdnxFd-om5qWt0toN4n10CRUuHSPxwNY5MdQg@mail.gmail.com>
Date: Wed, 2 Oct 2024 16:27:17 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: andrew@...n.ch, netdev@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	hkallweit1@...il.com, tmgross@...ch.edu, ojeda@...nel.org, 
	alex.gaynor@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	benno.lossin@...ton.me, a.hindborg@...sung.com
Subject: Re: [PATCH net-next v1 1/2] rust: add delay abstraction

On Wed, Oct 2, 2024 at 3:58 PM FUJITA Tomonori
<fujita.tomonori@...il.com> wrote:
>
> On Wed, 2 Oct 2024 14:37:55 +0200
> Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> > On Wed, Oct 2, 2024 at 2:19 PM Andrew Lunn <andrew@...n.ch> wrote:
> >>
> >> > > I would also document the units for the parameter. Is it picoseconds
> >> > > or centuries?
> >> >
> >> > Rust's Duration is created from seconds and nanoseconds.
> >>
> >> How well know is that? And is there a rust-for-linux wide preference
> >> to use Duration for time? Are we going to get into a situation that
> >> some abstractions use Duration, others seconds, some milliseconds,
> >> etc, just like C code?
> >>
> >> Anyway, i would still document the parameter is a Duration, since it
> >> is different to how C fsleep() works.
> >
> > I'm not necessarily convinced we want to use the Rust Duration type.
> > Similar questions came up when I added the Ktime type. The Rust
> > Duration type is rather large.
>
> core::mem::size_of::<core::time::Duration>() says 16 bytes.
>
> You prefer to add a simpler Duration structure to kernel/time.rs?
> Something like:
>
> struct Duration {
>     nanos: u64,
> }
>
> u64 in nanoseconds is enough for delay in the kernel, I think.

That type already exists. It's called kernel::time::Ktime.

Alice