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bpf: Prefer dirty packs for eBPF allocations

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The pack allocator only flushes predictors when reusing a dirty pack for
cBPF, eBPF allocations never trigger a flush. Currently, eBPF picks the
first free pack, which could be a clean pack. As an optimization, leaving
a clean pack for cBPF can avoid flushes.

Prefer dirty packs for eBPF and keep clean packs free for cBPF. This
mirrors the existing cBPF preference for clean packs: each program kind
prefers the pack that avoids an extra flush, and falls back to the other
kind only when no preferred pack has room. eBPF reuse of a dirty pack is
harmless since eBPF being privileged does not flush.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Pawan Gupta 2026-06-29 22:39:29 -07:00 committed by Daniel Borkmann
parent a9b1f19a6a
commit b72e29e0f7
1 changed files with 3 additions and 3 deletions
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6
kernel/bpf/core.c
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@ -988,10 +988,10 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns, bool
goto found_free_area;
/*
* cBPF reuse of a dirty pack triggers a flush, so prefer a
* clean pack for cBPF. eBPF never flushes, so pick the first
* free pack, dirty or clean.
* clean pack for cBPF. eBPF never flushes, so steer it to a
* dirty pack and keep clean packs free for cBPF.
*/
if (!was_classic || !pack->arch_flush_needed)
if (was_classic ^ pack->arch_flush_needed)
goto found_free_area;
if (!fallback_pack) {
fallback_pack = pack;