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Eduard Zingerman says: ==================== An overview of the register tracking liveness algorithm. Previous versions posted here: [1], [2], [3]. - Changes from RFC to v2 (suggested by Andrii Nakryiko): - wording corrected to use term "stack slot" instead of "stack spill"; - parentage chain diagram updated to show nil links for frame #1; - added example for non-BPF_DW writes behavior; - explanation in "Read marks propagation for cache hits" is reworked. - Changes from v2 to v3: - lot's of grammatical / wording fixes as suggested by David Vernet; - "Register parentage chains" section is fixed to reflect what happens to r1-r5 when function call is processed (as suggested by David and Alexei); - Example in "Liveness marks tracking" section updated to explain why partial writes should not lead to REG_LIVE_WRITTEN marks (suggested by David); - "Read marks propagation for cache hits" section updates: - Explanation updated to hint why read marks should be propagated before jumping to example (suggested by David); - Removed box around B/D in the diagram updated (suggested by Alexei). - Changes from v3 to v4 (suggested by Edward Cree): - register parentage chain diagram updated to explain why r6 mark is not propagated; - read mark propagation algorithm pseudo-code fixed to correctly show "if state->live & REG_LIVE_WRITTEN" stop condition; - general wording improvements in section "Liveness marks tracking". [1] https://lore.kernel.org/bpf/20230124220343.2942203-1-eddyz87@gmail.com/ [2] https://lore.kernel.org/bpf/20230130182400.630997-1-eddyz87@gmail.com/ [3] https://lore.kernel.org/bpf/20230131181118.733845-1-eddyz87@gmail.com/ ==================== Signed-off-by: Alexei Starovoitov <ast@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 Restructured Text 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.