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Mon, 26 Jan 2026 01:48:03 -0800 (PST) Received: from krava ([2a02:8308:a00c:e200::b44f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435b1f7b4d8sm27562381f8f.38.2026.01.26.01.48.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jan 2026 01:48:02 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 26 Jan 2026 10:48:01 +0100 To: Steven Rostedt Cc: Florent Revest , Andrii Nakryiko , Mark Rutland , 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: Re: [PATCHv6 bpf-next 0/9] ftrace,bpf: Use single direct ops for bpf trampolines Message-ID: References: <20251230145010.103439-1-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260126_014805_904487_C8B2B50F X-CRM114-Status: GOOD ( 32.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org hi, gentle ping, thanks jirka On Thu, Jan 15, 2026 at 10:54:09AM -0800, Andrii Nakryiko wrote: > On Tue, Dec 30, 2025 at 6:50 AM Jiri Olsa wrote: > > > > 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: https://lore.kernel.org/bpf/20251120212402.466524-1-jolsa@kernel.org/ > > v4: https://lore.kernel.org/bpf/20251203082402.78816-1-jolsa@kernel.org/ > > v5: https://lore.kernel.org/bpf/20251215211402.353056-10-jolsa@kernel.org/ > > > > v6 changes: > > - rename add_hash_entry_direct to add_ftrace_hash_entry_direct [Steven] > > - factor hash_add/hash_sub [Steven] > > - add kerneldoc header for update_ftrace_direct_* functions [Steven] > > - few assorted smaller fixes [Steven] > > - added missing direct_ops wrappers for !CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > > case [Steven] > > > > So this looks good from BPF side, I think. Steven, if you don't mind > giving this patch set another look and if everything is to your liking > giving your ack, we can then apply it to bpf-next. Thanks! > > > v5 changes: > > - do not export ftrace_hash object [Steven] > > - fix update_ftrace_direct_add new_filter_hash leak [ci] > > > > v4 changes: > > - rebased on top of bpf-next/master (with jmp attach changes) > > added patch 1 to deal with that > > - added extra checks for update_ftrace_direct_del/mod to address > > the ci bot review > > > > 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 (9): > > ftrace,bpf: Remove FTRACE_OPS_FL_JMP ftrace_ops flag > > 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 | 31 +++++++++- > > kernel/bpf/trampoline.c | 259 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------- > > kernel/trace/Kconfig | 3 + > > kernel/trace/ftrace.c | 406 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------- > > 6 files changed, 632 insertions(+), 75 deletions(-) > >