Re: [PATCH v2 02/18] perf test: Add workload-ctl option
From: Arnaldo Carvalho de Melo
Date: Wed Jun 03 2026 - 15:27:04 EST
On Wed, Jun 03, 2026 at 04:21:44PM -0300, Arnaldo Carvalho de Melo wrote:
> On Tue, Jun 02, 2026 at 03:26:44PM +0100, James Clark wrote:
> > Add a --workload-ctl=fifo:ctl-fifo[,ack-fifo] option for 'perf test
> > -w'. When set, run_workload() opens the named FIFO, writes enable before
> > invoking the builtin workload, writes disable before returning, and
> > waits for ack responses when an ack FIFO is provided to ensure that the
> > workload doesn't run until the events are enabled.
> >
> > This can be used to limit the scope of the recording to only the
> > workload execution and avoid recording Perf setup and teardown code if
> > Perf record is started with events disabled (-D 1).
>
> I see no mention to the equivalent in 'perf record', from its man page:
Nevermind, I should've read it completely :-\
- Arnaldo
> ----------------------------------------------------------------------
> --control=fifo:ctl-fifo[,ack-fifo]::
> --control=fd:ctl-fd[,ack-fd]::
> ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows.
> Listen on ctl-fd descriptor for command to control measurement.
>
> Available commands:
>
> - 'enable' : enable events
> - 'disable' : disable events
> - 'enable name' : enable event 'name'
> - 'disable name' : disable event 'name'
> - 'snapshot' : AUX area tracing snapshot).
> - 'stop' : stop perf record
> - 'ping' : ping
> - 'evlist [-v|-g|-F] : display all events
>
> -F Show just the sample frequency used for each event.
> -v Show all fields.
> -g Show event group information.
> ----------------------------------------------------------------------
>
> Can this be shared code?
>
> - Arnaldo
>
> > Assisted-by: Codex:GPT-5.5
> > Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
> > ---
> > tools/perf/Documentation/perf-test.txt | 6 ++
> > tools/perf/tests/builtin-test.c | 184 ++++++++++++++++++++++++++++++++-
> > 2 files changed, 188 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-test.txt b/tools/perf/Documentation/perf-test.txt
> > index 32da0d1fa86a..1faf30d4a7be 100644
> > --- a/tools/perf/Documentation/perf-test.txt
> > +++ b/tools/perf/Documentation/perf-test.txt
> > @@ -69,3 +69,9 @@ OPTIONS
> >
> > --list-workloads::
> > List the available workloads to use with -w/--workload.
> > +
> > +--workload-ctl=fifo:ctl-fifo[,ack-fifo]::
> > + Write 'enable' to ctl-fifo before running the workload and 'disable'
> > + before returning. If ack-fifo is provided, the workload runner waits for
> > + an 'ack' response after each command. This scopes the recording to only
> > + the workload if used with 'perf record -D 1 --control ...'.
> > diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> > index f2c135891477..d5df3efdce3b 100644
> > --- a/tools/perf/tests/builtin-test.c
> > +++ b/tools/perf/tests/builtin-test.c
> > @@ -50,6 +50,7 @@ static bool sequential;
> > static unsigned int runs_per_test = 1;
> > const char *dso_to_test;
> > const char *test_objdump_path = "objdump";
> > +static const char *workload_control;
> >
> > /*
> > * List of architecture specific tests. Not a weak symbol as the array length is
> > @@ -161,6 +162,11 @@ static struct test_workload *workloads[] = {
> > #endif
> > };
> >
> > +struct workload_control {
> > + int ctl_fd;
> > + int ack_fd;
> > +};
> > +
> > #define workloads__for_each(workload) \
> > for (unsigned i = 0; i < ARRAY_SIZE(workloads) && ({ workload = workloads[i]; 1; }); i++)
> >
> > @@ -711,13 +717,185 @@ static int workloads__fprintf_list(FILE *fp)
> > return printed;
> > }
> >
> > +static int perf_control_open_fifo(struct workload_control *ctl, const char *str)
> > +{
> > + char *s, *p;
> > + int ret;
> > +
> > + if (strncmp(str, "fifo:", 5))
> > + return -EINVAL;
> > +
> > + str += 5;
> > + if (!*str || *str == ',')
> > + return -EINVAL;
> > +
> > + s = strdup(str);
> > + if (!s)
> > + return -ENOMEM;
> > +
> > + p = strchr(s, ',');
> > + if (p)
> > + *p = '\0';
> > +
> > + ctl->ctl_fd = open(s, O_WRONLY | O_CLOEXEC);
> > + if (ctl->ctl_fd < 0) {
> > + ret = -errno;
> > + pr_err("Failed to open workload control FIFO '%s': %m\n", s);
> > + free(s);
> > + return ret;
> > + }
> > +
> > + if (p && *++p) {
> > + ctl->ack_fd = open(p, O_RDONLY | O_CLOEXEC);
> > + if (ctl->ack_fd < 0) {
> > + ret = -errno;
> > + pr_err("Failed to open workload control ack FIFO '%s': %m\n", p);
> > + close(ctl->ctl_fd);
> > + ctl->ctl_fd = -1;
> > + free(s);
> > + return ret;
> > + }
> > + }
> > +
> > + free(s);
> > + return 0;
> > +}
> > +
> > +static int perf_control_open(struct workload_control *ctl)
> > +{
> > + int ret;
> > +
> > + if (!workload_control)
> > + return 0;
> > +
> > + ret = perf_control_open_fifo(ctl, workload_control);
> > +
> > + if (ret == -EINVAL) {
> > + pr_err("Unsupported workload control spec '%s', expected fifo:ctl-fifo[,ack-fifo]\n",
> > + workload_control);
> > + }
> > +
> > + return ret;
> > +}
> > +
> > +static void perf_control_close(struct workload_control *ctl)
> > +{
> > + if (ctl->ctl_fd >= 0) {
> > + close(ctl->ctl_fd);
> > + ctl->ctl_fd = -1;
> > + }
> > + if (ctl->ack_fd >= 0) {
> > + close(ctl->ack_fd);
> > + ctl->ack_fd = -1;
> > + }
> > +}
> > +
> > +static int perf_control_write_cmd(int fd, const char *cmd)
> > +{
> > + size_t len = strlen(cmd);
> > + ssize_t ret;
> > +
> > + while (len) {
> > + ret = write(fd, cmd, len);
> > + if (ret < 0) {
> > + if (errno == EINTR)
> > + continue;
> > + pr_err("Failed to write perf control command '%s': %m\n", cmd);
> > + return -1;
> > + }
> > +
> > + if (!ret) {
> > + pr_err("Failed to write perf control command '%s': short write\n", cmd);
> > + return -1;
> > + }
> > +
> > + cmd += ret;
> > + len -= ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int perf_control_read_ack(int fd)
> > +{
> > + char buf[16];
> > + ssize_t ret;
> > +
> > + do {
> > + ret = read(fd, buf, sizeof(buf) - 1);
> > + } while (ret < 0 && errno == EINTR);
> > +
> > + if (ret < 0) {
> > + pr_err("Failed to read perf control ack: %m\n");
> > + return -1;
> > + }
> > +
> > + if (!ret) {
> > + pr_err("Unexpected EOF while reading perf control ack\n");
> > + return -1;
> > + }
> > +
> > + buf[ret] = '\0';
> > + for (ssize_t i = 0; i < ret; i++) {
> > + if (buf[i] == '\n' || buf[i] == '\0') {
> > + buf[i] = '\0';
> > + break;
> > + }
> > + }
> > +
> > + if (strcmp(buf, "ack")) {
> > + pr_err("Unexpected perf control ack: %s\n", buf);
> > + return -1;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int perf_control_send(struct workload_control *ctl, const char *cmd)
> > +{
> > + if (ctl->ctl_fd < 0)
> > + return 0;
> > +
> > + if (perf_control_write_cmd(ctl->ctl_fd, cmd))
> > + return -1;
> > +
> > + if (ctl->ack_fd >= 0 && perf_control_read_ack(ctl->ack_fd))
> > + return -1;
> > +
> > + return 0;
> > +}
> > +
> > static int run_workload(const char *work, int argc, const char **argv)
> > {
> > struct test_workload *twl;
> >
> > workloads__for_each(twl) {
> > - if (!strcmp(twl->name, work))
> > - return twl->func(argc, argv);
> > + struct workload_control ctl = {
> > + .ctl_fd = -1,
> > + .ack_fd = -1,
> > + };
> > + int control_ret, ret;
> > +
> > + if (strcmp(twl->name, work))
> > + continue;
> > +
> > + ret = perf_control_open(&ctl);
> > + if (ret)
> > + return ret;
> > +
> > + if (perf_control_send(&ctl, "enable\n")) {
> > + perf_control_close(&ctl);
> > + return -1;
> > + }
> > +
> > + ret = twl->func(argc, argv);
> > +
> > + control_ret = perf_control_send(&ctl, "disable\n");
> > + perf_control_close(&ctl);
> > + if (control_ret)
> > + return -1;
> > +
> > + return ret;
> > }
> >
> > pr_info("No workload found: %s\n", work);
> > @@ -799,6 +977,8 @@ int cmd_test(int argc, const char **argv)
> > OPT_UINTEGER('r', "runs-per-test", &runs_per_test,
> > "Run each test the given number of times, default 1"),
> > OPT_STRING('w', "workload", &workload, "work", "workload to run for testing, use '--list-workloads' to list the available ones."),
> > + OPT_STRING(0, "workload-ctl", &workload_control, "fifo:ctl-fifo[,ack-fifo]",
> > + "Write enable to the fifo just before running the workload and disable after, with optional ack from ack-fifo"),
> > OPT_BOOLEAN(0, "list-workloads", &list_workloads, "List the available builtin workloads to use with -w/--workload"),
> > OPT_STRING(0, "dso", &dso_to_test, "dso", "dso to test"),
> > OPT_STRING(0, "objdump", &test_objdump_path, "path",
> >
> > --
> > 2.34.1