mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-02 15:43:35 -04:00
7e3811cb99
Convert profiler[123].c to "volatile compare" to compare barrier_var() approach vs bpf_cmp_likely() vs bpf_cmp_unlikely(). bpf_cmp_unlikely() produces correct code, but takes much longer to verify: ./veristat -C -e prog,insns,states before after_with_unlikely Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ------------------------------------ --------- --------- ------------------ ---------- ---------- ----------------- kprobe__proc_sys_write 1603 19606 +18003 (+1123.08%) 123 1678 +1555 (+1264.23%) kprobe__vfs_link 11815 70305 +58490 (+495.05%) 971 4967 +3996 (+411.53%) kprobe__vfs_symlink 5464 42896 +37432 (+685.07%) 434 3126 +2692 (+620.28%) kprobe_ret__do_filp_open 5641 44578 +38937 (+690.25%) 446 3162 +2716 (+608.97%) raw_tracepoint__sched_process_exec 2770 35962 +33192 (+1198.27%) 226 3121 +2895 (+1280.97%) raw_tracepoint__sched_process_exit 1526 2135 +609 (+39.91%) 133 208 +75 (+56.39%) raw_tracepoint__sched_process_fork 265 337 +72 (+27.17%) 19 24 +5 (+26.32%) tracepoint__syscalls__sys_enter_kill 18782 140407 +121625 (+647.56%) 1286 12176 +10890 (+846.81%) bpf_cmp_likely() is equivalent to barrier_var(): ./veristat -C -e prog,insns,states before after_with_likely Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ------------------------------------ --------- --------- -------------- ---------- ---------- ------------- kprobe__proc_sys_write 1603 1663 +60 (+3.74%) 123 127 +4 (+3.25%) kprobe__vfs_link 11815 12090 +275 (+2.33%) 971 971 +0 (+0.00%) kprobe__vfs_symlink 5464 5448 -16 (-0.29%) 434 426 -8 (-1.84%) kprobe_ret__do_filp_open 5641 5739 +98 (+1.74%) 446 446 +0 (+0.00%) raw_tracepoint__sched_process_exec 2770 2608 -162 (-5.85%) 226 216 -10 (-4.42%) raw_tracepoint__sched_process_exit 1526 1526 +0 (+0.00%) 133 133 +0 (+0.00%) raw_tracepoint__sched_process_fork 265 265 +0 (+0.00%) 19 19 +0 (+0.00%) tracepoint__syscalls__sys_enter_kill 18782 18970 +188 (+1.00%) 1286 1286 +0 (+0.00%) kprobe__proc_sys_write 2700 2809 +109 (+4.04%) 107 109 +2 (+1.87%) kprobe__vfs_link 12238 12366 +128 (+1.05%) 267 269 +2 (+0.75%) kprobe__vfs_symlink 7139 7365 +226 (+3.17%) 167 175 +8 (+4.79%) kprobe_ret__do_filp_open 7264 7070 -194 (-2.67%) 180 182 +2 (+1.11%) raw_tracepoint__sched_process_exec 3768 3453 -315 (-8.36%) 211 199 -12 (-5.69%) raw_tracepoint__sched_process_exit 3138 3138 +0 (+0.00%) 83 83 +0 (+0.00%) raw_tracepoint__sched_process_fork 265 265 +0 (+0.00%) 19 19 +0 (+0.00%) tracepoint__syscalls__sys_enter_kill 26679 24327 -2352 (-8.82%) 1067 1037 -30 (-2.81%) kprobe__proc_sys_write 1833 1833 +0 (+0.00%) 157 157 +0 (+0.00%) kprobe__vfs_link 9995 10127 +132 (+1.32%) 803 803 +0 (+0.00%) kprobe__vfs_symlink 5606 5672 +66 (+1.18%) 451 451 +0 (+0.00%) kprobe_ret__do_filp_open 5716 5782 +66 (+1.15%) 462 462 +0 (+0.00%) raw_tracepoint__sched_process_exec 3042 3042 +0 (+0.00%) 278 278 +0 (+0.00%) raw_tracepoint__sched_process_exit 1680 1680 +0 (+0.00%) 146 146 +0 (+0.00%) raw_tracepoint__sched_process_fork 299 299 +0 (+0.00%) 25 25 +0 (+0.00%) tracepoint__syscalls__sys_enter_kill 18372 18372 +0 (+0.00%) 1558 1558 +0 (+0.00%) default (mcpu=v3), no_alu32, cpuv4 have similar differences. Note one place where bpf_nop_mov() is used to workaround the verifier lack of link between the scalar register and its spill to stack. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20231226191148.48536-7-alexei.starovoitov@gmail.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.