From patchwork Fri Aug 9 19:23:57 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13759172 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 302B22B9A9; Fri, 9 Aug 2024 19:24:01 +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=1723231442; cv=none; b=q8sSuHY7AYRsa3U31Pxtpxz/4r3P8Wu+iCUqPP2AdPVo7dghurK5b74gDTzUaF+LJQN2AaGb6w1aRPe8YFAfCu91N6KZlXM9Bwu+2PyO5VWb2bzadn5cnKB8qDTwBtZPrAMGaLvGU53+Tgs94/y9V6ZNETYmW+jTKoX6c/XHKH8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723231442; c=relaxed/simple; bh=zmnG5xSUMyo+9plaKeJ+uvQbkZxCdb3QwwtYbn++p1Y=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=XNcJtlxBT1A9cFt9VA+c9js5zVLh0U1dVh5bX2bHfrjPnIl0bMpMGLJau215Ci7JNzJsMt/ao8jSHrr3I1qEKNqaTgE5k/d1wm0xEHglXDg82ROFe/5uT4lyfiPzkIfR5u8hpujNUC/kkvIWBP+8jof/qvXcwrt2bTVf4Qan4/c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rAzhLSna; 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="rAzhLSna" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92A98C4AF0D; Fri, 9 Aug 2024 19:24:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723231441; bh=zmnG5xSUMyo+9plaKeJ+uvQbkZxCdb3QwwtYbn++p1Y=; h=From:To:Cc:Subject:Date:From; b=rAzhLSnad0hcaVB+vG8FglY5NDsl00xiqannTJyJ7R1OMaf4orx6nYpKJh3i71R/C cfKPqVlLNRVn7177R+UCaiRxkPaJzknGOP6Z4qZd/pOPFafE0+oCed7+qAVFKz6Oa7 ZStMgAwLoPNGYNPKrucxFDObkQJJXrD5Dqz4lvbb9X7BzV5pPN0Nd9brC69aSPPVun zZ5pu+O+I0UoPysQL4K5+2FLhlGbB1MgTxXjcB0bJxWs2kIOOLQCTUY+SlL2EFBwh6 77lZVx6iJBni56wlWiJ4jsYwMqMLq3Wwf1++WDARkzXOh1b0uZkfclJ23+EvX1SKxs hBhBXuIrA89ew== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org Cc: peterz@infradead.org, oleg@redhat.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, Andrii Nakryiko Subject: [PATCH v2] uprobes: make trace_uprobe->nhit counter a per-CPU one Date: Fri, 9 Aug 2024 12:23:57 -0700 Message-ID: <20240809192357.4061484-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 trace_uprobe->nhit counter is not incremented atomically, so its value is questionable in when uprobe is hit on multiple CPUs simultaneously. Also, doing this shared counter increment across many CPUs causes heavy cache line bouncing, limiting uprobe/uretprobe performance scaling with number of CPUs. Solve both problems by making this a per-CPU counter. Signed-off-by: Andrii Nakryiko Reviewed-by: Oleg Nesterov --- kernel/trace/trace_uprobe.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 52e76a73fa7c..002f801a7ab4 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "trace_dynevent.h" #include "trace_probe.h" @@ -62,7 +63,7 @@ struct trace_uprobe { struct uprobe *uprobe; unsigned long offset; unsigned long ref_ctr_offset; - unsigned long nhit; + unsigned long __percpu *nhits; struct trace_probe tp; }; @@ -337,6 +338,12 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret) if (!tu) return ERR_PTR(-ENOMEM); + tu->nhits = alloc_percpu(unsigned long); + if (!tu->nhits) { + ret = -ENOMEM; + goto error; + } + ret = trace_probe_init(&tu->tp, event, group, true, nargs); if (ret < 0) goto error; @@ -349,6 +356,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret) return tu; error: + free_percpu(tu->nhits); kfree(tu); return ERR_PTR(ret); @@ -362,6 +370,7 @@ static void free_trace_uprobe(struct trace_uprobe *tu) path_put(&tu->path); trace_probe_cleanup(&tu->tp); kfree(tu->filename); + free_percpu(tu->nhits); kfree(tu); } @@ -815,13 +824,21 @@ static int probes_profile_seq_show(struct seq_file *m, void *v) { struct dyn_event *ev = v; struct trace_uprobe *tu; + unsigned long nhits; + int cpu; if (!is_trace_uprobe(ev)) return 0; tu = to_trace_uprobe(ev); + + nhits = 0; + for_each_possible_cpu(cpu) { + nhits += READ_ONCE(*per_cpu_ptr(tu->nhits, cpu)); + } + seq_printf(m, " %s %-44s %15lu\n", tu->filename, - trace_probe_name(&tu->tp), tu->nhit); + trace_probe_name(&tu->tp), nhits); return 0; } @@ -1507,7 +1524,8 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs) int ret = 0; tu = container_of(con, struct trace_uprobe, consumer); - tu->nhit++; + + this_cpu_inc(*tu->nhits); udd.tu = tu; udd.bp_addr = instruction_pointer(regs);