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author | Hou Tao <houtao1@huawei.com> | 2024-01-05 11:48:17 +0100 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2024-01-23 23:40:21 +0100 |
commit | 7c05e7f3e74e7e550534d524e04d7e6f78d6fa24 (patch) | |
tree | 83d12bcddc908580f8bc73f5572ddeda96561665 /arch/x86/net/bpf_jit_comp.c | |
parent | Merge branch 'inet_diag-remove-three-mutexes-in-diag-dumps' (diff) | |
download | linux-7c05e7f3e74e7e550534d524e04d7e6f78d6fa24.tar.xz linux-7c05e7f3e74e7e550534d524e04d7e6f78d6fa24.zip |
bpf: Support inlining bpf_kptr_xchg() helper
The motivation of inlining bpf_kptr_xchg() comes from the performance
profiling of bpf memory allocator benchmark. The benchmark uses
bpf_kptr_xchg() to stash the allocated objects and to pop the stashed
objects for free. After inling bpf_kptr_xchg(), the performance for
object free on 8-CPUs VM increases about 2%~10%. The inline also has
downside: both the kasan and kcsan checks on the pointer will be
unavailable.
bpf_kptr_xchg() can be inlined by converting the calling of
bpf_kptr_xchg() into an atomic_xchg() instruction. But the conversion
depends on two conditions:
1) JIT backend supports atomic_xchg() on pointer-sized word
2) For the specific arch, the implementation of xchg is the same as
atomic_xchg() on pointer-sized words.
It seems most 64-bit JIT backends satisfies these two conditions. But
as a precaution, defining a weak function bpf_jit_supports_ptr_xchg()
to state whether such conversion is safe and only supporting inline for
64-bit host.
For x86-64, it supports BPF_XCHG atomic operation and both xchg() and
atomic_xchg() use arch_xchg() to implement the exchange, so enabling the
inline of bpf_kptr_xchg() on x86-64 first.
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20240105104819.3916743-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/x86/net/bpf_jit_comp.c')
-rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 919f647c740f..e1390d1e331b 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -3242,3 +3242,8 @@ void bpf_arch_poke_desc_update(struct bpf_jit_poke_descriptor *poke, BUG_ON(ret < 0); } } + +bool bpf_jit_supports_ptr_xchg(void) +{ + return true; +} |