ceac059ed4
For binaries that are statically linked, consecutive stack frames are likely to be in the same VMA and therefore have the same build id. On a real-world workload, we observed that 66% of CPU cycles in __bpf_get_stackid() were spent on build_id_parse() and find_vma(). As an optimization for this case, we can cache the previous frame's VMA, if the new frame has the same VMA as the previous one, reuse the previous one's build id. We are holding the MM locks as reader across the entire loop, so we don't need to worry about VMA going away. Tested through "stacktrace_build_id" and "stacktrace_build_id_nmi" in test_progs. Suggested-by: Greg Thelen <gthelen@google.com> Signed-off-by: Hao Luo <haoluo@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/bpf/20220224000531.1265030-1-haoluo@google.com
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.