Implement perf stat --control for cgi#22537
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perf stat --control allows the profiled process to enable and disable counters
at runtime. This allows us to skip profiling startup and shutdown for more
accurate results. The same already exists for valgrind.
$ perf stat -D -1 --control fifo:/tmp/perfctl,/tmp/perfack
-D -1 starts perf stat with counters disabled. --control makes perf stat connect
to the /tmp/perfctl and /tmp/perfack fifo files. These need to exist when
starting perf, so create them using mkfifo /tmp/perf{ctl,ack}. The ctl fifo is
written to by cgi to enable/disable counters, whereas the ack fifo is written to
by perf stat to acknolwedge counters have been installed.
Additionally, you'll need to set the set the PERF_STAT_CTL_FIFO and
PERF_STAT_ACK_FIFO env variables for cgi to find the fifo files.
arnaud-lb
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Looks good to me otherwise!
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| if (ctl_fd == -2) { | ||
| ctl_fd = zps_open_fifo(ZPS_CTL_FIFO_ENV, O_WRONLY); | ||
| } | ||
| if (ack_fd == -2) { | ||
| ack_fd = zps_open_fifo(ZPS_ACK_FIFO_ENV, O_RDONLY); | ||
| } |
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For ease of debugging we should print an error message and exit when these functions fail while the env vars are set
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| for (ssize_t i = 0; i < bytes_read; i++) { | ||
| if (ack[i] == '\n') { | ||
| return; | ||
| } | ||
| } |
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We can likely omit this loop and just check that we have read strlen("ack\n") in total
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Switched the loop to just drain the pipe, that avoids potential synchronization issues.
Just drain the pipe.
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perf stat --controlallows the profiled process to enable and disable counters at runtime. This allows us to skip profiling startup and shutdown for more accurate results. The same already exists for valgrind.-D -1startsperf statwith counters disabled.--controlmakesperf statconnect to the/tmp/perfctland/tmp/perfackfifo files. These need to exist when starting perf, so create them usingmkfifo /tmp/perf{ctl,ack}. The ctl fifo is written to by cgi to enable/disable counters, whereas the ack fifo is written to byperf statto acknolwedge counters have been installed.Additionally, you'll need to set the set the
PERF_STAT_CTL_FIFOandPERF_STAT_ACK_FIFOenv variables for cgi to find the fifo files.Split off from iluuu1994#218.