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cpumf/pai: Add command line option for realtime scheduling

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Pai collects data from per CPU ring buffers and stores them in the
memory mapped output file. When data is collected from many CPUs at
the same time, writing data to output file can be slow.
Improve this and allow the pai recording to run with higher
real time priority. This is the same approach as done by the perf tool.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
This commit is contained in:
Thomas Richter
2023-11-07 09:51:55 +01:00
committed by Steffen Eiden
parent a3cb877c54
commit d2b5e1e2d6
2 changed files with 33 additions and 0 deletions
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12
cpumf/man/pai.8
View File

@@ -18,6 +18,8 @@
.IR size ]
.RB [ \-i | \-\-interval
.IR ms ]
.RB [ \-R | \-\-realtime
.IR prio ]
.BR \-c | \-\-crypto [ \fIcpulist ][: \fIdata\fR "] [" \fIloops\fP ]
.br
\*c
@@ -25,6 +27,8 @@
.IR size ]
.RB [ \-i | \-\-interval
.IR ms ]
.RB [ \-R | \-\-realtime
.IR prio ]
.BR \-n | \-\-nnpa [ \fIcpulist ][: \fIdata\fR "] [" \fIloops\fP ]
.br
\*c
@@ -191,6 +195,14 @@ The ring buffer is created with the
.IR mmap (2)
system call.
.
.TP
.BR \-R ", " \-\-realtime "\ prio"
Collect data using the RT SCHED_FIFO priority specified by
.BR prio .
Valid values are integers in the range 1 (low) to 99 (high).
Use this option when gathering data from multiple CPUs
to prevent data loss.
.
.SH ARGUMENT
The command line options determine how command line
arguments are interpreted.

21
cpumf/pai.c
View File

@@ -944,6 +944,11 @@ static struct util_opt opt_vec[] = {
.option = { "report", no_argument, NULL, 'r' },
.desc = "Report file contents"
},
{
.option = { "realtime", required_argument, NULL, 'R' },
.argument = "PRIO",
.desc = "Collect data with this RT SCHED_FIFO priority"
},
{
.option = { "interval", required_argument, NULL, 'i' },
.argument = "NUMBER",
@@ -1007,6 +1012,19 @@ static unsigned long check_mapsize(unsigned long n)
return cnt == 1 ? n : 0;
}
static void setprio(const char *prio)
{
struct sched_param param;
char *endstr;
memset(&param, 0, sizeof(param));
param.sched_priority = strtoul(prio, &endstr, 0);
if (*endstr)
errno = EINVAL;
if (*endstr || sched_setscheduler(0, SCHED_FIFO, &param))
err(EXIT_FAILURE, "Could not set realtime priority");
}
int main(int argc, char **argv)
{
bool crypto_record = false, report = false;
@@ -1061,6 +1079,9 @@ int main(int argc, char **argv)
record_cpus_nnpa(optarg);
nnpa_record = true;
break;
case 'R':
setprio(optarg);
break;
case 'r':
report = true;
break;