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From: Gal Pressman <gal@nvidia.com>
To: Shay Agroskin <shayagr@amazon.com>,
	David Miller <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org
Cc: "Woodhouse, David" <dwmw@amazon.com>,
	"Machulsky, Zorik" <zorik@amazon.com>,
	"Matushevsky, Alexander" <matua@amazon.com>,
	Saeed Bshara <saeedb@amazon.com>, "Wilson, Matt" <msw@amazon.com>,
	"Liguori, Anthony" <aliguori@amazon.com>,
	"Bshara, Nafea" <nafea@amazon.com>,
	"Belgazal, Netanel" <netanel@amazon.com>,
	"Saidi, Ali" <alisaidi@amazon.com>,
	"Herrenschmidt, Benjamin" <benh@amazon.com>,
	"Kiyanovski, Arthur" <akiyano@amazon.com>,
	"Dagan, Noam" <ndagan@amazon.com>,
	"Arinzon, David" <darinzon@amazon.com>,
	"Itzko, Shahar" <itzko@amazon.com>,
	"Abboud, Osama" <osamaabb@amazon.com>
Subject: Re: [PATCH v4 net-next 1/5] ethtool: Add support for configuring tx_push_buf_len
Date: Thu, 9 Mar 2023 19:15:43 +0200	[thread overview]
Message-ID: <316ee596-e184-8613-d136-cd2cb13a589f@nvidia.com> (raw)
In-Reply-To: <20230309131319.2531008-2-shayagr@amazon.com>

On 09/03/2023 15:13, Shay Agroskin wrote:
> +``ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN`` specifies the maximum number of bytes of a
> +transmitted packet a driver can push directly to the underlying device
> +('push' mode). Pushing some of the payload bytes to the device has the
> +advantages of reducing latency for small packets by avoiding DMA mapping (same
> +as ``ETHTOOL_A_RINGS_TX_PUSH`` parameter) as well as allowing the underlying
> +device to process packet headers ahead of fetching its payload.
> +This can help the device to make fast actions based on the packet's headers.

I know Jakub prefers the new parameter, but the description of this
still sounds extremely similar to TX copybreak to me..
TX copybreak was traditionally used to copy packets to preallocated DMA
buffers, but this could be implemented as copying the packet to the
(preallocated) WQE's inline part. That usually means DMA memory, but
could also be device memory in this ENA LLQ case.

Are we drawing a line that TX copybreak is the threshold for DMA memory
and tx_push_buf_len is the threshold for device memory?
Are they mutually exclusive?

BTW, as I mentioned in v1, ENA doesn't advertise tx_push, which is a bit
strange given the fact that it now adds tx_push_buf_len support.

  parent reply	other threads:[~2023-03-09 17:18 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-09 13:13 [PATCH v4 net-next 0/5] Add tx push buf len param to ethtool Shay Agroskin
2023-03-09 13:13 ` [PATCH v4 net-next 1/5] ethtool: Add support for configuring tx_push_buf_len Shay Agroskin
2023-03-09 16:25   ` Simon Horman
2023-03-09 17:15   ` Gal Pressman [this message]
2023-03-10  6:53     ` Jakub Kicinski
2023-03-12 12:41       ` Gal Pressman
2023-03-13 19:09         ` Jakub Kicinski
2023-03-14 15:38           ` Shay Agroskin
2023-03-16 11:57             ` Gal Pressman
2023-03-16 20:42               ` Jakub Kicinski
2023-03-14 15:46     ` Shay Agroskin
2023-03-09 13:13 ` [PATCH v4 net-next 2/5] net: ena: Make few cosmetic preparations to support large LLQ Shay Agroskin
2023-03-09 16:28   ` Simon Horman
2023-03-09 13:13 ` [PATCH v4 net-next 3/5] net: ena: Add an option to configure large LLQ headers Shay Agroskin
2023-03-09 16:28   ` Simon Horman
2023-03-09 13:13 ` [PATCH v4 net-next 4/5] net: ena: Recalculate TX state variables every device reset Shay Agroskin
2023-03-09 13:13 ` [PATCH v4 net-next 5/5] net: ena: Add support to changing tx_push_buf_len Shay Agroskin
2023-03-09 16:28   ` Simon Horman
2023-03-10  6:54   ` Jakub Kicinski

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