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4485166519
Jiong Wang says:
====================
Currently, compiler will lower memcpy function call in XDP/eBPF C program
into a sequence of eBPF load/store pairs for some scenarios.
Compiler is thinking this "inline" optimiation is beneficial as it could
avoid function call and also increase code locality.
However, Netronome NPU is not an tranditional load/store architecture that
doing a sequence of individual load/store actions are not efficient.
This patch set tries to identify the load/store sequences composed of
load/store pairs that comes from memcpy lowering, then accelerates them
through NPU's Command Push Pull (CPP) instruction.
This patch set registered an new optimization pass before doing the actual
JIT work, it traverse through eBPF IR, once found candidate sequence then
record the memory copy source, destination and length information in the
first load instruction starting the sequence and marks all remaining
instructions in the sequence into skipable status. Later, when JITing the
first load instructoin, optimal instructions will be generated using those
record information.
For this safety of this transformation:
- jump into the middle of the sequence will cancel the optimization.
- overlapped memory access will cancel the optimization.
- the load destination register still contains the same value as before
the transformation.
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.