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23dc986732
cpumap takes RX processing out of softirq and onto a separate kthread.
Since the kthread needs to be scheduled in order to run (versus softirq
which does not), we can theoretically experience extra latency if the
system is under load and the scheduler is being unfair to us.
Moving the tracepoint to before passing the skb list up the stack allows
users to more accurately measure enqueue/dequeue latency introduced by
cpumap via xdp:xdp_cpumap_enqueue and xdp:xdp_cpumap_kthread tracepoints.
f9419f7bd7 ("bpf: cpumap add tracepoints") which added the tracepoints
states that the intent behind them was for general observability and for
a feedback loop to see if the queues are being overwhelmed. This change
does not mess with either of those use cases but rather adds a third
one.
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://lore.kernel.org/bpf/47615d5b5e302e4bd30220473779e98b492d47cd.1725585718.git.dxu@dxuuu.xyz
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.