From patchwork Mon Aug 5 20:28:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13754051 X-Patchwork-Delegate: mhiramat@kernel.org 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 11F1413CF86; Mon, 5 Aug 2024 20:28:06 +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=1722889687; cv=none; b=ZcQ18ZutdLprh6yamQkgLjWeQTiL8B6lz7y8WiWmmQly3Vy1uG66LNPtrG4Sym0fa334eMDT5K6pL4175KU7skAxkJA2SnY0dh0VCa5QNnPzoADMstP9W5dUL8gTMASw+fj52cdHT/NcbczbzxN9MAEObJXUVYgqlB9YLZzRhfY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722889687; c=relaxed/simple; bh=ytY7BCZ4p2pRVE1pUSq3YppSwfqJsmzi1njORzdxIsY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=attGLNE8c5kJec4InT6/8sZTjNCoSC6jsXDlXlFaiBSWNKaZcLXorkhQIQ2Kw9iQ4eMZyBIh3MPb2dVzNKwpA8V3gJQE3XDc31ZlDnc97a/h8oe957TuCP13T0nP9S8PPli3flUwwVPSrJtMeWZ+pmqpkWUlCS6utg1+J8Y5JTQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uhhgPl2h; 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="uhhgPl2h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86837C32782; Mon, 5 Aug 2024 20:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722889686; bh=ytY7BCZ4p2pRVE1pUSq3YppSwfqJsmzi1njORzdxIsY=; h=From:To:Cc:Subject:Date:From; b=uhhgPl2hxbczZSJ38YXHEb1HEMak8s2WUStfRl7N4gC/6KSU69dvtqG1nk+Tgz6Xw OkEEEuaDOe5auHupuciNn5WInJU3dUE56txJaFuRXypLQr+bv/cKDgVEOQWpg8YEXP EeHtqqtaa3pv5CAF3oK2TMHRYor6fTpNL6popAeLFkW2zmXoNb1Ee+MgOBrqomRhmh QU1wrzhzHLSFOz0+Q+ZhqZ2kOn0G7F8oKFv03dHv8gVub3pvIqk/3wG7WBM4lofi6w QUTNk1xZDH+KqrwV59c7q9xm8CiFvEtoX0s4RawdITS/r8yMlc2Wd1bvt2dC/14J6A 35y5Lox9SzM7w== 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] uprobes: get rid of bogus trace_uprobe hit counter Date: Mon, 5 Aug 2024 13:28:03 -0700 Message-ID: <20240805202803.1813090-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: linux-trace-kernel@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 bogus in practice. On the other hand, it's actually a pretty big uprobe scalability problem due to heavy cache line bouncing between CPUs triggering the same uprobe. Drop it and emit obviously unrealistic value in its stead in uporbe_profiler seq file. The alternative would be allocating per-CPU counter, but I'm not sure it's justified. Signed-off-by: Andrii Nakryiko --- kernel/trace/trace_uprobe.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 52e76a73fa7c..5d38207db479 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -62,7 +62,6 @@ struct trace_uprobe { struct uprobe *uprobe; unsigned long offset; unsigned long ref_ctr_offset; - unsigned long nhit; struct trace_probe tp; }; @@ -821,7 +820,7 @@ static int probes_profile_seq_show(struct seq_file *m, void *v) tu = to_trace_uprobe(ev); seq_printf(m, " %s %-44s %15lu\n", tu->filename, - trace_probe_name(&tu->tp), tu->nhit); + trace_probe_name(&tu->tp), ULONG_MAX); return 0; } @@ -1507,7 +1506,6 @@ 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++; udd.tu = tu; udd.bp_addr = instruction_pointer(regs);