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CONFIG_INIT_STACK_ALL_ZERO introduces a performance cost by
zero-initializing all stack variables on function entry. The mlx5 XDP
RX path previously allocated a struct mlx5e_xdp_buff on the stack per
received CQE, resulting in measurable performance degradation under
this config.
This patch reuses a mlx5e_xdp_buff stored in the mlx5e_rq struct,
avoiding per-CQE stack allocations and repeated zeroing.
With this change, XDP_DROP and XDP_TX performance matches that of
kernels built without CONFIG_INIT_STACK_ALL_ZERO.
Performance was measured on a ConnectX-6Dx using a single RX channel
(1 CPU at 100% usage) at ~50 Mpps. The baseline results were taken from
net-next-6.15.
Stack zeroing disabled:
- XDP_DROP:
* baseline: 31.47 Mpps
* baseline + per-RQ allocation: 32.31 Mpps (+2.68%)
- XDP_TX:
* baseline: 12.41 Mpps
* baseline + per-RQ allocation: 12.95 Mpps (+4.30%)
Stack zeroing enabled:
- XDP_DROP:
* baseline: 24.32 Mpps
* baseline + per-RQ allocation: 32.27 Mpps (+32.7%)
- XDP_TX:
* baseline: 11.80 Mpps
* baseline + per-RQ allocation: 12.24 Mpps (+3.72%)
Reported-by: Sebastiano Miano <mianosebastiano@gmail.com>
Reported-by: Samuel Dobron <sdobron@redhat.com>
Link: https://lore.kernel.org/all/CAMENy5pb8ea+piKLg5q5yRTMZacQqYWAoVLE1FE9WhQPq92E0g@mail.gmail.com/
Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://patch.msgid.link/1747253032-663457-1-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.