Messages in this thread Patch in this message | | | Date | Fri, 14 Aug 2020 08:53:18 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v8 04/18] perf ftrace: add option '-m/--buffer-size' to set per-cpu buffer size |
| |
Em Sat, Aug 08, 2020 at 10:31:27AM +0800, Changbin Du escreveu: > This adds an option '-m/--buffer-size' to allow us set the size of per-cpu > tracing buffer. > > Signed-off-by: Changbin Du <changbin.du@gmail.com>
So this is a little bit confusing, i.e. if I don't specify a suffix (B, K, M, G) I get:
# perf ftrace -m 2048
Usage: perf ftrace [<options>] [<command>] or: perf ftrace [<options>] -- <command> [<options>]
-m, --buffer-size <size> size of per cpu buffer #
Which is not very helpful, and you also forgot to add an entry to 'man perf-ftrace' (tools/perf/Documentation/perf-ftrace.txt), so only by looking at the patch I was able to figure out that a suffix is required.
Now look how 'perf trace' works:
# perf trace -m 2048 -e open* --max-events 1 0.772 sh/343169 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: RDONLY|CLOEXEC) = 3 #
I.e. it doesn't require a unit suffix, which is more natural.
# perf trace -h -m
-m, --mmap-pages <pages> number of mmap data pages
#
It indicates that the argument is in units of 'pages', while you don't state that in: $ perf ftrace -h -m -m, --buffer-size <size> size of per cpu buffer $
So please improve the option description and add its longer explanation in the man page, also I suggest you interpret:
# perf ftrace -m 2048
as asking for 2048K since the file as _kb in its name, so people used to ftrace will get what they ask for, i.e. N kb. Please add this to the one line description in 'perf ftrace -h', namely that the default unit os 'K'.
All this can be made on top of this series, so I'm applying it now to make progress.
- Arnaldo
> --- > v2: support units as a suffix. > --- > tools/perf/Documentation/perf-ftrace.txt | 5 +++ > tools/perf/builtin-ftrace.c | 55 ++++++++++++++++++++++++ > 2 files changed, 60 insertions(+) > > diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt > index 4f5628445a63..7a5d915f60b0 100644 > --- a/tools/perf/Documentation/perf-ftrace.txt > +++ b/tools/perf/Documentation/perf-ftrace.txt > @@ -53,6 +53,11 @@ OPTIONS > Ranges of CPUs are specified with -: 0-2. > Default is to trace on all online CPUs. > > +-m:: > +--buffer-size:: > + Set the size of per-cpu tracing buffer, <size> is expected to > + be a number with appended unit character - B/K/M/G. > + > -T:: > --trace-funcs=:: > Select function tracer and set function filter on the given > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c > index 4b3fcee5725a..a3a4f4be9dde 100644 > --- a/tools/perf/builtin-ftrace.c > +++ b/tools/perf/builtin-ftrace.c > @@ -26,6 +26,7 @@ > #include "thread_map.h" > #include "util/cap.h" > #include "util/config.h" > +#include "util/units.h" > > #define DEFAULT_TRACER "function_graph" > > @@ -39,6 +40,7 @@ struct perf_ftrace { > struct list_head graph_funcs; > struct list_head nograph_funcs; > int graph_depth; > + unsigned long percpu_buffer_size; > }; > > struct filter_entry { > @@ -324,6 +326,21 @@ static int set_tracing_depth(struct perf_ftrace *ftrace) > return 0; > } > > +static int set_tracing_percpu_buffer_size(struct perf_ftrace *ftrace) > +{ > + int ret; > + > + if (ftrace->percpu_buffer_size == 0) > + return 0; > + > + ret = write_tracing_file_int("buffer_size_kb", > + ftrace->percpu_buffer_size / 1024); > + if (ret < 0) > + return ret; > + > + return 0; > +} > + > static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv) > { > char *trace_file; > @@ -388,6 +405,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv) > goto out_reset; > } > > + if (set_tracing_percpu_buffer_size(ftrace) < 0) { > + pr_err("failed to set tracing per-cpu buffer size\n"); > + goto out_reset; > + } > + > if (write_tracing_file("current_tracer", ftrace->tracer) < 0) { > pr_err("failed to set current_tracer to %s\n", ftrace->tracer); > goto out_reset; > @@ -506,6 +528,37 @@ static void delete_filter_func(struct list_head *head) > } > } > > +static int parse_buffer_size(const struct option *opt, > + const char *str, int unset) > +{ > + unsigned long *s = (unsigned long *)opt->value; > + static struct parse_tag tags_size[] = { > + { .tag = 'B', .mult = 1 }, > + { .tag = 'K', .mult = 1 << 10 }, > + { .tag = 'M', .mult = 1 << 20 }, > + { .tag = 'G', .mult = 1 << 30 }, > + { .tag = 0 }, > + }; > + unsigned long val; > + > + if (unset) { > + *s = 0; > + return 0; > + } > + > + val = parse_tag_value(str, tags_size); > + if (val != (unsigned long) -1) { > + if (val < 1024) { > + pr_err("buffer size too small, must larger than 1KB."); > + return -1; > + } > + *s = val; > + return 0; > + } > + > + return -1; > +} > + > static void select_tracer(struct perf_ftrace *ftrace) > { > bool graph = !list_empty(&ftrace->graph_funcs) || > @@ -560,6 +613,8 @@ int cmd_ftrace(int argc, const char **argv) > "Set nograph filter on given functions", parse_filter_func), > OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth, > "Max depth for function graph tracer"), > + OPT_CALLBACK('m', "buffer-size", &ftrace.percpu_buffer_size, "size", > + "size of per cpu buffer", parse_buffer_size), > OPT_END() > }; > > -- > 2.25.1 >
--
- Arnaldo
| |