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verifier.c:is_state_visited() uses RANGE_WITHIN states comparison rules for cached states that have loop_entry with non-zero branches count (meaning that loop_entry's verification is not yet done). The RANGE_WITHIN rules in regsafe()/stacksafe() require register and stack objects types to be identical in current and old states. verifier.c:clean_live_states() replaces registers and stack spills with NOT_INIT/STACK_INVALID marks, if these registers/stack spills are not read in any child state. This means that clean_live_states() works against loop convergence logic under some conditions. See selftest in the next patch for a specific example. Mitigate this by prohibiting clean_verifier_state() when state->loop_entry->branches > 0. This undoes negative verification performance impact of the copy_verifier_state() fix from the previous patch. Below is comparison between master and current patch. selftests: File Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ---------------------------------- ---------------------------- --------- --------- --------------- ---------- ---------- -------------- arena_htab.bpf.o arena_htab_llvm 717 423 -294 (-41.00%) 57 37 -20 (-35.09%) arena_htab_asm.bpf.o arena_htab_asm 597 445 -152 (-25.46%) 47 37 -10 (-21.28%) arena_list.bpf.o arena_list_add 1493 1822 +329 (+22.04%) 30 37 +7 (+23.33%) arena_list.bpf.o arena_list_del 309 261 -48 (-15.53%) 23 15 -8 (-34.78%) iters.bpf.o checkpoint_states_deletion 18125 22154 +4029 (+22.23%) 818 918 +100 (+12.22%) iters.bpf.o iter_nested_deeply_iters 593 367 -226 (-38.11%) 67 43 -24 (-35.82%) iters.bpf.o iter_nested_iters 813 772 -41 (-5.04%) 79 72 -7 (-8.86%) iters.bpf.o iter_subprog_check_stacksafe 155 135 -20 (-12.90%) 15 14 -1 (-6.67%) iters.bpf.o iter_subprog_iters 1094 808 -286 (-26.14%) 88 68 -20 (-22.73%) iters.bpf.o loop_state_deps2 479 356 -123 (-25.68%) 46 35 -11 (-23.91%) iters.bpf.o triple_continue 35 31 -4 (-11.43%) 3 3 +0 (+0.00%) kmem_cache_iter.bpf.o open_coded_iter 63 59 -4 (-6.35%) 7 6 -1 (-14.29%) mptcp_subflow.bpf.o _getsockopt_subflow 501 446 -55 (-10.98%) 25 23 -2 (-8.00%) pyperf600_iter.bpf.o on_event 12339 6379 -5960 (-48.30%) 441 286 -155 (-35.15%) verifier_bits_iter.bpf.o max_words 92 84 -8 (-8.70%) 8 7 -1 (-12.50%) verifier_iterating_callbacks.bpf.o cond_break2 113 192 +79 (+69.91%) 12 21 +9 (+75.00%) sched_ext: File Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ----------------- ---------------------- --------- --------- ----------------- ---------- ---------- ---------------- bpf.bpf.o layered_dispatch 11485 9039 -2446 (-21.30%) 848 662 -186 (-21.93%) bpf.bpf.o layered_dump 7422 5022 -2400 (-32.34%) 681 298 -383 (-56.24%) bpf.bpf.o layered_enqueue 16854 13753 -3101 (-18.40%) 1611 1308 -303 (-18.81%) bpf.bpf.o layered_init 1000001 5549 -994452 (-99.45%) 84672 523 -84149 (-99.38%) bpf.bpf.o layered_runnable 3149 1899 -1250 (-39.70%) 288 151 -137 (-47.57%) bpf.bpf.o p2dq_init 2343 1936 -407 (-17.37%) 201 170 -31 (-15.42%) bpf.bpf.o refresh_layer_cpumasks 16487 1285 -15202 (-92.21%) 1770 120 -1650 (-93.22%) bpf.bpf.o rusty_select_cpu 1937 1386 -551 (-28.45%) 177 125 -52 (-29.38%) scx_central.bpf.o central_dispatch 636 600 -36 (-5.66%) 63 59 -4 (-6.35%) scx_central.bpf.o central_init 913 632 -281 (-30.78%) 48 39 -9 (-18.75%) scx_nest.bpf.o nest_init 636 601 -35 (-5.50%) 60 58 -2 (-3.33%) scx_pair.bpf.o pair_dispatch 1000001 1914 -998087 (-99.81%) 58169 142 -58027 (-99.76%) scx_qmap.bpf.o qmap_dispatch 2393 2187 -206 (-8.61%) 196 174 -22 (-11.22%) scx_qmap.bpf.o qmap_init 16367 22777 +6410 (+39.16%) 603 768 +165 (+27.36%) 'layered_init' and 'pair_dispatch' hit 1M on master, but are verified ok with this patch. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250215110411.3236773-4-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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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.