Messages in this thread | | | Date | Thu, 12 Jan 2023 18:59:25 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/4] tracing: Add creation of instances at boot command line |
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On Thu, 12 Jan 2023 16:24:17 -0700 Ross Zwisler <zwisler@google.com> wrote:
> On Wed, Jan 11, 2023 at 09:56:37AM -0500, Steven Rostedt wrote: > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > > > Add kernel command line to add tracing instances. This only creates > > instances at boot but still does not enable any events to them. Later > > changes will extend this command line to add enabling of events, filters, > > and triggers. As well as possibly redirecting trace_printk()! > > > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > --- > > .../admin-guide/kernel-parameters.txt | 6 +++ > > kernel/trace/trace.c | 51 +++++++++++++++++++ > > 2 files changed, 57 insertions(+) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 6cfa6e3996cf..cec486217ccc 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -6272,6 +6272,12 @@ > > comma-separated list of trace events to enable. See > > also Documentation/trace/events.rst > > > > + trace_instance=[instance-info] > > + [FTRACE] Create an ring buffer instance early in boot up. > > + This will be listed in: > > + > > + /sys/kernel/tracing/instances > > Should this be "/sys/kernel/debug/tracing/instances"?
No, the /sys/kernel/debug/tracing is deprecated. It only exists for backward compatibility. If it's still in documentation, it should be updated.
> > Ditto for the text for 'ftrace_boot_snapshot': > > ftrace_boot_snapshot > [FTRACE] On boot up, a snapshot will be taken of the > ftrace ring buffer that can be read at: > /sys/kernel/tracing/snapshot. > > Everywhere else we use /sys/kernel/debug/tracing, though we do use > /sys/kernel/tracing in Documentation/trace/ftrace.txt ?
Right, that's because it was missed when I was updating it ;-)
All documentation that references /sys/kernel/debug/tracing should be replaced with /sys/kernel/tracing.
> > I guess either works, but having just 1 or the other will help us not confuse > users.
Agreed. Want to send a clean up patch? ;-)
> > > + > > trace_options=[option-list] > > [FTRACE] Enable or disable tracer options at boot. > > The option-list is a comma delimited list of options > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index a555a861b978..34ed504ffca9 100644 > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -48,6 +48,9 @@ > > #include <linux/fsnotify.h> > > #include <linux/irq_work.h> > > #include <linux/workqueue.h> > > +#include <linux/workqueue.h> > > Duplicate include 1 line above.
Good catch.
> > > + > > +#include <asm/setup.h> /* COMMAND_LINE_SIZE */ > > > > #include "trace.h" > > #include "trace_output.h" > > @@ -186,6 +189,9 @@ static char *default_bootup_tracer; > > static bool allocate_snapshot; > > static bool snapshot_at_boot; > > > > +static char boot_instance_info[COMMAND_LINE_SIZE] __initdata; > > +static int boot_instance_index; > > + > > static int __init set_cmdline_ftrace(char *str) > > { > > strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE); > > @@ -239,6 +245,23 @@ static int __init boot_snapshot(char *str) > > __setup("ftrace_boot_snapshot", boot_snapshot); > > > > > > +static int __init boot_instance(char *str) > > +{ > > + char *slot = boot_instance_info + boot_instance_index; > > + int left = COMMAND_LINE_SIZE - boot_instance_index; > > A bit safer to use sizeof(boot_instance_info) instead of COMMAND_LINE_SIZE, > so we can change the allocation size of boot_instance_info without having to > keep them in sync.
Either way is fine. I wouldn't make this change if it was the only thing I needed to fix, but as I need to get rid of the extra "workqueue.h", I can make this change too.
> > These are mostly nits, you can add: > > Reviewed-by: Ross Zwisler <zwisler@google.com>
Thanks!
-- Steve
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