Tool perf has a couple of sub commands. There are a couple of issues around counter enabling time point. In addition, we want a precise time clock when collect system-wide or process/thread-wide statistics.
I worked out 3 patches against tips/master tree of March 17 to fix such issues and enhance perf to be more user-friendly. Subject: [PATCH 1/3] perf events: Enable counters when collecting process-wide or system-wide data by 'perf stat' From: Zhang, Yanmin <[email protected]> Command 'perf stat' doesn't enable counters when collecting an existing (by -p) process or a system-wide statistics. Fix the issue. Change the condition of fork/exec subcommand. If there is a subcommand parameter, perf always fork/exec it. The usage example is: #perf stat -a sleep 10 So this command could collect statistics for 10 seconds precisely. User still could stop it by CTRL+C. Without the new capability, user could only use CTRL+C to stop it without precise time clock. Another issue is 'perf stat -a' consumes 100% time of a full single logical cpu. It has a bad impact on running workload. Fix it by adding a sleep(1) in the while(!done) loop in function run_perf_stat. Signed-off-by: Zhang Yanmin <[email protected]> --- diff -Nraup linux-2.6_tipmaster0317/tools/perf/builtin-stat.c linux-2.6_tipmaster0317_fixstat/tools/perf/builtin-stat.c --- linux-2.6_tipmaster0317/tools/perf/builtin-stat.c 2010-03-18 09:04:40.938289813 +0800 +++ linux-2.6_tipmaster0317_fixstat/tools/perf/builtin-stat.c 2010-03-18 13:07:26.773773541 +0800 @@ -159,8 +159,10 @@ static void create_perf_stat_counter(int } } else { attr->inherit = inherit; - attr->disabled = 1; - attr->enable_on_exec = 1; + if (target_pid == -1) { + attr->disabled = 1; + attr->enable_on_exec = 1; + } fd[0][counter] = sys_perf_event_open(attr, pid, -1, -1, 0); if (fd[0][counter] < 0 && verbose) @@ -251,9 +253,9 @@ static int run_perf_stat(int argc __used unsigned long long t0, t1; int status = 0; int counter; - int pid = target_pid; + int pid; int child_ready_pipe[2], go_pipe[2]; - const bool forks = (target_pid == -1 && argc > 0); + const bool forks = (argc > 0); char buf; if (!system_wide) @@ -265,10 +267,10 @@ static int run_perf_stat(int argc __used } if (forks) { - if ((pid = fork()) < 0) + if ((child_pid = fork()) < 0) perror("failed to fork"); - if (!pid) { + if (!child_pid) { close(child_ready_pipe[0]); close(go_pipe[1]); fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC); @@ -297,8 +299,6 @@ static int run_perf_stat(int argc __used exit(-1); } - child_pid = pid; - /* * Wait for the child to be ready to exec. */ @@ -309,6 +309,10 @@ static int run_perf_stat(int argc __used close(child_ready_pipe[0]); } + if (target_pid == -1) + pid = child_pid; + else + pid = target_pid; for (counter = 0; counter < nr_counters; counter++) create_perf_stat_counter(counter, pid); @@ -321,7 +325,7 @@ static int run_perf_stat(int argc __used close(go_pipe[1]); wait(&status); } else { - while(!done); + while(!done) sleep(1); } t1 = rdclock(); @@ -459,7 +463,7 @@ static volatile int signr = -1; static void skip_signal(int signo) { - if(target_pid != -1) + if(child_pid == -1) done = 1; signr = signo; -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
