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From: "Danilo Krummrich" <dakr@kernel.org>
To: "Eliot Courtney" <ecourtney@nvidia.com>
Cc: "Alice Ryhl" <aliceryhl@google.com>,
	"Alexandre Courbot" <acourbot@nvidia.com>,
	"David Airlie" <airlied@gmail.com>,
	"Simona Vetter" <simona@ffwll.ch>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Boqun Feng" <boqun@kernel.org>, "Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <lossin@kernel.org>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Trevor Gross" <tmgross@umich.edu>, "Zhi Wang" <zhiw@nvidia.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Alistair Popple" <apopple@nvidia.com>,
	"Joel Fernandes" <joelagnelf@nvidia.com>,
	"Timur Tabi" <ttabi@nvidia.com>,
	nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org
Subject: Re: [PATCH v5 2/9] gpu: nova-core: gsp: add mechanism to wait for space on command queue
Date: Wed, 04 Mar 2026 12:39:08 +0100	[thread overview]
Message-ID: <DGTYVZMRVLLE.3HQVL7ZT6MU7H@kernel.org> (raw)
In-Reply-To: <20260304-cmdq-continuation-v5-2-3f19d759ed93@nvidia.com>

On Wed Mar 4, 2026 at 2:42 AM CET, Eliot Courtney wrote:
> +    fn allocate_command(&mut self, size: usize, timeout: Delta) -> Result<GspCommand<'_>> {
> +        read_poll_timeout(
> +            || Ok(self.driver_write_area_size()),
> +            |available_bytes| *available_bytes >= size_of::<GspMsgElement>() + size,
> +            Delta::ZERO,

Isn't this either creating unneccessary thrashing of the memory controller or
unnecessary contention at the cache-coherency level?

I think we should probably add at least a small delay of something around 1us.

> +            timeout,
> +        )?;

  reply	other threads:[~2026-03-04 11:39 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-04  1:42 [PATCH v5 0/9] gpu: nova-core: gsp: add continuation record support Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 1/9] gpu: nova-core: gsp: sort `MsgFunction` variants alphabetically Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 2/9] gpu: nova-core: gsp: add mechanism to wait for space on command queue Eliot Courtney
2026-03-04 11:39   ` Danilo Krummrich [this message]
2026-03-05  7:37     ` Eliot Courtney
2026-03-05  7:50       ` John Hubbard
2026-03-05  8:01         ` Eliot Courtney
2026-03-05 10:38       ` Alexandre Courbot
2026-03-05 11:16       ` Danilo Krummrich
2026-03-06  0:48         ` Alexandre Courbot
2026-03-06  1:46           ` Gary Guo
2026-03-06 11:03           ` Danilo Krummrich
2026-03-06  5:21         ` Alexandre Courbot
2026-03-04  1:42 ` [PATCH v5 3/9] rust: add EMSGSIZE error code Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 4/9] gpu: nova-core: gsp: add checking oversized commands Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 5/9] gpu: nova-core: gsp: clarify invariant on command queue Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 6/9] gpu: nova-core: gsp: unconditionally call variable payload handling Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 7/9] gpu: nova-core: gsp: add `size_in_bytes` helper to `CommandToGsp` Eliot Courtney
2026-03-04  2:53   ` Alexandre Courbot
2026-03-04  3:10     ` Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 8/9] gpu: nova-core: gsp: support large RPCs via continuation record Eliot Courtney
2026-03-04  1:42 ` [PATCH v5 9/9] gpu: nova-core: gsp: add tests for continuation records Eliot Courtney

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