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 1DBC91D6A2 for ; Mon, 11 Dec 2023 12:46:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Syringvq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5ADEC433C7; Mon, 11 Dec 2023 12:46:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702298791; bh=JQ2o4bswOLI0VG1kbn//h0fFBpjxy8snq+Qxqqghh0s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Syringvqd/XP6XWsNwRyFQTfhiFBvxhD9hHTce4bs4W53HSKyqeyBhiZ8U8vLTSgi 7HMuSoh5JkyMEG48+MYby+085nLqTc60sxzo9MOZLzTssL7kiEqEIsGDdv1hURSwHP 4D/k+r7i3vgVe7XioX8URQkE0m2SSNnXeOFOT0BMAqZY+cEYiM0SDjCpaUPe9E7ZTZ aVRsu5+jmw0qft9Jfcou9OJEe0n2gG0gpX72YfxKlQYmHlVO8kTirj8pBy60ha4xtn qjVBMzQFVgxkzks6KsD6CvApglj3h08xCm91G3dQqW8FjtH/N9zgEjV0Mkn5umEasj J4y/00m0kkagg== Date: Mon, 11 Dec 2023 21:46:27 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: LKML , Linux Trace Kernel , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers Subject: Re: [PATCH] trace_seq: Increase the buffer size to almost two pages Message-Id: <20231211214627.cff4ecfead14029ef22cd3ef@kernel.org> In-Reply-To: <20231209175220.19867af4@gandalf.local.home> References: <20231209175220.19867af4@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 9 Dec 2023 17:52:20 -0500 Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > Now that trace_marker can hold more than 1KB string, and can write as much > as the ring buffer can hold, the trace_seq is not big enough to hold > writes: > > ~# a="1234567890" > ~# cnt=4080 > ~# s="" > ~# while [ $cnt -gt 10 ]; do > ~# s="${s}${a}" > ~# cnt=$((cnt-10)) > ~# done > ~# echo $s > trace_marker > ~# cat trace > # tracer: nop > # > # entries-in-buffer/entries-written: 2/2 #P:8 > # > # _-----=> irqs-off/BH-disabled > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / _-=> migrate-disable > # |||| / delay > # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > # | | | ||||| | | > <...>-860 [002] ..... 105.543465: tracing_mark_write[LINE TOO BIG] > <...>-860 [002] ..... 105.543496: tracing_mark_write: 789012345678901234567890 > > By increasing the trace_seq buffer to almost two pages, it can now print > out the first line. > > This also subtracts the rest of the trace_seq fields from the buffer, so > that the entire trace_seq is now PAGE_SIZE aligned. Ok, but I just a bit concern about the memory consumption. Since this is very specific case, can we make it configurable later? Reviewed-by: Masami Hiramatsu (Google) Thanks, > > Signed-off-by: Steven Rostedt (Google) > --- > include/linux/trace_seq.h | 9 ++++++--- > kernel/trace/trace.c | 6 +++--- > kernel/trace/trace_seq.c | 3 --- > 3 files changed, 9 insertions(+), 9 deletions(-) > > diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h > index 3691e0e76a1a..9ec229dfddaa 100644 > --- a/include/linux/trace_seq.h > +++ b/include/linux/trace_seq.h > @@ -8,11 +8,14 @@ > > /* > * Trace sequences are used to allow a function to call several other functions > - * to create a string of data to use (up to a max of PAGE_SIZE). > + * to create a string of data to use. > */ > > +#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \ > + (sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int))) > + > struct trace_seq { > - char buffer[PAGE_SIZE]; > + char buffer[TRACE_SEQ_BUFFER_SIZE]; > struct seq_buf seq; > size_t readpos; > int full; > @@ -21,7 +24,7 @@ struct trace_seq { > static inline void > trace_seq_init(struct trace_seq *s) > { > - seq_buf_init(&s->seq, s->buffer, PAGE_SIZE); > + seq_buf_init(&s->seq, s->buffer, TRACE_SEQ_BUFFER_SIZE); > s->full = 0; > s->readpos = 0; > } > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 83393c65ec71..da837119a446 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -3753,7 +3753,7 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str, > > /* OK if part of the temp seq buffer */ > if ((addr >= (unsigned long)iter->tmp_seq.buffer) && > - (addr < (unsigned long)iter->tmp_seq.buffer + PAGE_SIZE)) > + (addr < (unsigned long)iter->tmp_seq.buffer + TRACE_SEQ_BUFFER_SIZE)) > return true; > > /* Core rodata can not be freed */ > @@ -6926,8 +6926,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, > goto out; > } > > - if (cnt >= PAGE_SIZE) > - cnt = PAGE_SIZE - 1; > + if (cnt >= TRACE_SEQ_BUFFER_SIZE) > + cnt = TRACE_SEQ_BUFFER_SIZE - 1; > > /* reset all but tr, trace, and overruns */ > trace_iterator_reset(iter); > diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c > index 7be97229ddf8..c158d65a8a88 100644 > --- a/kernel/trace/trace_seq.c > +++ b/kernel/trace/trace_seq.c > @@ -13,9 +13,6 @@ > * trace_seq_init() more than once to reset the trace_seq to start > * from scratch. > * > - * The buffer size is currently PAGE_SIZE, although it may become dynamic > - * in the future. > - * > * A write to the buffer will either succeed or fail. That is, unlike > * sprintf() there will not be a partial write (well it may write into > * the buffer but it wont update the pointers). This allows users to > -- > 2.42.0 > -- Masami Hiramatsu (Google)