linux-kernel - Re: [PATCH 1/7] trace: Move trace_seq

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Date:   Wed, 15 Mar 2017 19:27:57 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/7] trace: Move trace_seq_overflowed out of line

On Wed, Mar 15, 2017 at 08:54:20PM -0400, Steven Rostedt wrote:
> On Tue, 14 Mar 2017 19:14:25 -0700
> Andi Kleen <andi@...stfloor.org> wrote:
> 
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > Inlining trace_seq_overflowed takes ~17k in text size in my kernel.
> > The function doesn't seem to be time critical, so we can just out of line it.
> 
> Instead of out of lining trace_seq_has_overflowed(), have you tried to
> out of line the function that's called by tracepoints (one per
> tracepoint). That is, trace_handle_return()?

This is a data driven approach so I always went for the largest savings.

> 
> The trace_seq_handle_overflow() is used in not reproduced places that I
> would like to keep it as an inline. If the issue is size of the kernel,

I cannot parse this sentence. What advantage has it being inline?

> please just out of line the one place that calls it that is duplicated
> for every tracepoint. Which happens to be trace_handle_return().

It is used in lots of places outside trace_handle_return, so that would
give far less savings.

-Andi

include/linux/trace_events.h:143:       return trace_seq_has_overflowed(s) ?
include/linux/trace_seq.h:60: * trace_seq_has_overflowed - return true if the trace_seq took too much
include/linux/trace_seq.h:66:static inline bool trace_seq_has_overflowed(struct trace_seq *s)
kernel/trace/ring_buffer.c:47:  return !trace_seq_has_overflowed(s);
kernel/trace/ring_buffer.c:390: return !trace_seq_has_overflowed(s);
kernel/trace/trace.c:3268:      if (trace_seq_has_overflowed(s))
kernel/trace/trace.c:3292:      if (trace_seq_has_overflowed(s))
kernel/trace/trace.c:3318:              if (trace_seq_has_overflowed(s))
kernel/trace/trace.c:3347:              if (trace_seq_has_overflowed(s))
kernel/trace/trace.c:3399:              if (trace_seq_has_overflowed(&iter->seq))
kernel/trace/trace.c:5490:              if (trace_seq_has_overflowed(&iter->seq)) {
kernel/trace/trace_functions_graph.c:910:       if (trace_seq_has_overflowed(s))
kernel/trace/trace_functions_graph.c:1221:      if (trace_seq_has_overflowed(s))
kernel/trace/trace_output.c:354:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:374:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:435:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:522:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:550:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:586:        return !trace_seq_has_overflowed(s);
kernel/trace/trace_output.c:1021:               if (trace_seq_has_overflowed(s))
kernel/trace/trace_output.c:1071:               if (ip == ULONG_MAX || trace_seq_has_overflowed(s))
kernel/trace/trace_probe.c:44:  return !trace_seq_has_overflowed(s);                            \
kernel/trace/trace_probe.c:73:  return !trace_seq_has_overflowed(s);
kernel/trace/trace_syscalls.c:147:              if (trace_seq_has_overflowed(s))