From: Yunlong Song <yunlong.s...@huawei.com> Although the memory of pid_to_task can be allocated via calloc according to the value of /proc/sys/kernel/pid_max, it cannot handle the case when pid_max is changed after 'perf sched record' has created its perf.data.
If the new pid_max configured in 'perf sched replay' is smaller than the old pid_max configured in 'perf sched record', then it will cause the assertion failure problem. To solve this problem, we realloc the memory of pid_to_task stepwise once the passed-in pid parameter in register_pid is larger than the current pid_max. Example: Test environment: x86_64 with 160 cores $ cat /proc/sys/kernel/pid_max 163840 $ perf sched record ls $ echo 5000 > /proc/sys/kernel/pid_max $ cat /proc/sys/kernel/pid_max 5000 Before this patch: $ perf sched replay run measurement overhead: 221 nsecs sleep measurement overhead: 55356 nsecs the run test took 1000011 nsecs the sleep test took 1060940 nsecs perf: builtin-sched.c:337: register_pid: Assertion `!(pid >= (unsigned long)pid_max)' failed. Aborted After this patch: $ perf sched replay run measurement overhead: 221 nsecs sleep measurement overhead: 55611 nsecs the run test took 1000026 nsecs the sleep test took 1060486 nsecs nr_run_events: 10 nr_sleep_events: 1562 nr_wakeup_events: 5 task 0 ( :1: 1), nr_events: 1 task 1 ( :2: 2), nr_events: 1 task 2 ( :3: 3), nr_events: 1 task 3 ( :5: 5), nr_events: 1 ... Signed-off-by: Yunlong Song <yunlong.s...@huawei.com> Cc: Paul Mackerras <pau...@samba.org> Cc: Peter Zijlstra <a.p.zijls...@chello.nl> Cc: Wang Nan <wangn...@huawei.com> Link: http://lkml.kernel.org/r/1427809596-29559-5-git-send-email-yunlong.s...@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com> --- tools/perf/builtin-sched.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index 20d887b222e4..dd714818fa4d 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -334,7 +334,12 @@ static struct task_desc *register_pid(struct perf_sched *sched, pid_max = MAX_PID; BUG_ON((sched->pid_to_task = calloc(pid_max, sizeof(struct task_desc *))) == NULL); } - BUG_ON(pid >= (unsigned long)pid_max); + if (pid >= (unsigned long)pid_max) { + BUG_ON((sched->pid_to_task = realloc(sched->pid_to_task, (pid + 1) * + sizeof(struct task_desc *))) == NULL); + while (pid >= (unsigned long)pid_max) + sched->pid_to_task[pid_max++] = NULL; + } task = sched->pid_to_task[pid]; -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
