From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 361F7309EE0; Thu, 20 Nov 2025 21:24:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763673853; cv=none; b=GdDl2+4qKW/TB7+rmPoUUT+Wo6soFZU4vWnnxxhdgKzKmblXhnTTMaINqz34iuxWIucLdHJuWPgkJyLMy3k8WxwV28w3vqb+UaImHHXqAG0zbl3kZSfOclTiWF6H3L0aZAwECC82hJoqMZPFZl89N+QU/Kk4roDLe4cRruypi7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763673853; c=relaxed/simple; bh=4Y8r/6ty+KwQSyf1uJgttUHp2wq+e/5lt08/NAvm/u0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=S43KUHeoTGFEkwix+o7CjSibHfluF8vNGymf9414JqyayLn4yB/x47lUsvow/J0+ewH455aFhE8j/EXD2wwqO0W+rG6yaILAwyN+gzqhTPlhjSy8jMdVX8LVgOK7XFrrZWYhphqqzdzlwS/4dKtIWjOivp7SKfjMqQSjsdnukos= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ivcmt+4Z; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ivcmt+4Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4B04C4CEF1; Thu, 20 Nov 2025 21:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763673852; bh=4Y8r/6ty+KwQSyf1uJgttUHp2wq+e/5lt08/NAvm/u0=; h=From:To:Cc:Subject:Date:From; b=Ivcmt+4ZsjqlDy79/NuPdPgc6lzXqtlHNT9fAgqWiK+5KvRrFRA22XrsSGL3QfCkC YwYSQLEM48sZt+t2TgN8miH00hi8FmmulYFjoGwyXbHkpvmzowMpqlZ1LEeVuxMyVy CLnsWPcsUAcN5YrwoFy9WPUXWKkR6uLm7NYf3sm4Eau5NfUGquwkRIKpvHM7JvAKGz 9cEBzzuZOqo4gFwnApCzk+/jIC/t1sAoub+McPU7/cxERjYsCf7QZSobLE6gRnD0H2 l8E34fJMSltjgVz8G4Ja8LVZmISycSlQiReQSZkPCDoqfuShScskP1gMPLhFfr4MB7 tFy94sW8tCQ6g== From: Jiri Olsa To: Steven Rostedt , Florent Revest , Mark Rutland Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Menglong Dong , Song Liu Subject: [PATCHv3 bpf-next 0/8] ftrace,bpf: Use single direct ops for bpf trampolines Date: Thu, 20 Nov 2025 22:23:54 +0100 Message-ID: <20251120212402.466524-1-jolsa@kernel.org> X-Mailer: git-send-email 2.51.1 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit hi, while poking the multi-tracing interface I ended up with just one ftrace_ops object to attach all trampolines. This change allows to use less direct API calls during the attachment changes in the future code, so in effect speeding up the attachment. In current code we get a speed up from using just a single ftrace_ops object. - with current code: Performance counter stats for 'bpftrace -e fentry:vmlinux:ksys_* {} -c true': 6,364,157,902 cycles:k 828,728,902 cycles:u 1,064,803,824 instructions:u # 1.28 insn per cycle 23,797,500,067 instructions:k # 3.74 insn per cycle 4.416004987 seconds time elapsed 0.164121000 seconds user 1.289550000 seconds sys - with the fix: Performance counter stats for 'bpftrace -e fentry:vmlinux:ksys_* {} -c true': 6,535,857,905 cycles:k 810,809,429 cycles:u 1,064,594,027 instructions:u # 1.31 insn per cycle 23,962,552,894 instructions:k # 3.67 insn per cycle 1.666961239 seconds time elapsed 0.157412000 seconds user 1.283396000 seconds sys The speedup seems to be related to the fact that with single ftrace_ops object we don't call ftrace_shutdown anymore (we use ftrace_update_ops instead) and we skip the synchronize rcu calls (each ~100ms) at the end of that function. rfc: https://lore.kernel.org/bpf/20250729102813.1531457-1-jolsa@kernel.org/ v1: https://lore.kernel.org/bpf/20250923215147.1571952-1-jolsa@kernel.org/ v2: https://lore.kernel.org/bpf/20251113123750.2507435-1-jolsa@kernel.org/ v3 changes: - rebased on top of bpf-next/master - fixed update_ftrace_direct_del cleanup path - added missing inline to update_ftrace_direct_* stubs v2 changes: - rebased on top fo bpf-next/master plus Song's livepatch fixes [1] - renamed the API functions [2] [Steven] - do not export the new api [Steven] - kept the original direct interface: I'm not sure if we want to melt both *_ftrace_direct and the new interface into single one. It's bit different in semantic (hence the name change as Steven suggested [2]) and I don't think the changes are not that big so we could easily keep both APIs. v1 changes: - make the change x86 specific, after discussing with Mark options for arm64 [Mark] thanks, jirka [1] https://lore.kernel.org/bpf/20251027175023.1521602-1-song@kernel.org/ [2] https://lore.kernel.org/bpf/20250924050415.4aefcb91@batman.local.home/ --- Jiri Olsa (8): ftrace: Make alloc_and_copy_ftrace_hash direct friendly ftrace: Export some of hash related functions ftrace: Add update_ftrace_direct_add function ftrace: Add update_ftrace_direct_del function ftrace: Add update_ftrace_direct_mod function bpf: Add trampoline ip hash table ftrace: Factor ftrace_ops ops_func interface bpf, x86: Use single ftrace_ops for direct calls arch/x86/Kconfig | 1 + include/linux/bpf.h | 7 ++- include/linux/ftrace.h | 37 +++++++++++++- kernel/bpf/trampoline.c | 205 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------ kernel/trace/Kconfig | 3 ++ kernel/trace/ftrace.c | 337 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- kernel/trace/trace.h | 8 --- 7 files changed, 547 insertions(+), 51 deletions(-)