Re: [PATCH 3/9] perf sched replay: Alloc the memory of pid_to_task dynamically to adapt to the unexpected change of pid_max

[David Ahern <dsahern@gmail.com>]

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On 3/31/15 7:46 AM, Yunlong Song wrote:
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index c466104..20d887b 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -23,6 +23,7 @@
>   #include <semaphore.h>
>   #include <pthread.h>
>   #include <math.h>
> +#include <api/fs/fs.h>
>
>   #define PR_SET_NAME		15               /* Set process name */
>   #define MAX_CPUS		4096
> @@ -124,7 +125,7 @@ struct perf_sched {
>   	struct perf_tool tool;
>   	const char	 *sort_order;
>   	unsigned long	 nr_tasks;
> -	struct task_desc *pid_to_task[MAX_PID];
> +	struct task_desc **pid_to_task;
>   	struct task_desc **tasks;
>   	const struct trace_sched_handler *tp_handler;
>   	pthread_mutex_t	 start_work_mutex;
> @@ -326,8 +327,14 @@ static struct task_desc *register_pid(struct perf_sched *sched,
>   				      unsigned long pid, const char *comm)
>   {
>   	struct task_desc *task;
> +	static int pid_max;
>
> -	BUG_ON(pid >= MAX_PID);
> +	if (sched->pid_to_task == NULL) {
> +		if (sysctl__read_int("kernel/pid_max", &pid_max) < 0)
> +			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);
>

so why the previous patch bumping the MAX_PID count if you move to 
dynamic here? And shouldn't MAX_PID get dropped here as well?

So attached is what i put together last week; just have not had time to 
send it out.

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>From 159dc732e0ad66d9151e93761bc9c685872e9fa4 Mon Sep 17 00:00:00 2001
From: David Ahern <david.ahern@oracle.com>
Date: Tue, 24 Mar 2015 16:57:10 -0400
Subject: [PATCH 3/5] perf sched: Remove max pid assumption from perf-sched

'perf sched replay' currently fails on sparc64:
    $ perf sched replay
    run measurement overhead: 2475 nsecs
    sleep measurement overhead: 56165 nsecs
    the run test took 999705 nsecs
    the sleep test took 1059270 nsecs
    perf: builtin-sched.c:384: register_pid: Assertion `!(pid >= 65536)' failed.
    Aborted

The max pid limitation is removed by converting pid_to_task from a
pid based array to an intlist (rblist) with the pid as the index
and task_desc stored in the priv element.

In the process pid is converted from a long int to int.

Signed-off-by: David Ahern <david.ahern@oracle.com>
---
 tools/perf/builtin-sched.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index cc52c993a1fa..858d85396d81 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -33,13 +33,12 @@
 #define MAX_CPUS		4096
 #define COMM_LEN		20
 #define SYM_LEN			129
-#define MAX_PID			65536
 
 struct sched_atom;
 
 struct task_desc {
 	unsigned long		nr;
-	unsigned long		pid;
+	int			pid;
 	char			comm[COMM_LEN];
 
 	unsigned long		nr_events;
@@ -129,7 +128,7 @@ struct perf_sched {
 	struct perf_tool tool;
 	const char	 *sort_order;
 	unsigned long	 nr_tasks;
-	struct task_desc *pid_to_task[MAX_PID];
+	struct intlist	 *pid_to_task;
 	struct task_desc **tasks;
 	const struct trace_sched_handler *tp_handler;
 	pthread_mutex_t	 start_work_mutex;
@@ -377,14 +376,18 @@ static void add_sched_event_sleep(struct perf_sched *sched, struct task_desc *ta
 }
 
 static struct task_desc *register_pid(struct perf_sched *sched,
-				      unsigned long pid, const char *comm)
+				      int pid, const char *comm)
 {
-	struct task_desc *task;
 
-	BUG_ON(pid >= MAX_PID);
+	struct int_node *node = intlist__findnew(sched->pid_to_task, pid);
+	struct task_desc *task;
 
-	task = sched->pid_to_task[pid];
+	if (node == NULL) {
+		pr_err("Failed to allocate entry for task\n");
+		return NULL;
+	}
 
+	task = (struct task_desc *) node->priv;
 	if (task)
 		return task;
 
@@ -392,20 +395,21 @@ static struct task_desc *register_pid(struct perf_sched *sched,
 	task->pid = pid;
 	task->nr = sched->nr_tasks;
 	strcpy(task->comm, comm);
+
 	/*
 	 * every task starts in sleeping state - this gets ignored
 	 * if there's no wakeup pointing to this sleep state:
 	 */
 	add_sched_event_sleep(sched, task, 0, 0);
 
-	sched->pid_to_task[pid] = task;
+	node->priv = task;
 	sched->nr_tasks++;
 	sched->tasks = realloc(sched->tasks, sched->nr_tasks * sizeof(struct task_task *));
 	BUG_ON(!sched->tasks);
 	sched->tasks[task->nr] = task;
 
 	if (verbose)
-		printf("registered task #%ld, PID %ld (%s)\n", sched->nr_tasks, pid, comm);
+		printf("registered task #%ld, PID %d (%s)\n", sched->nr_tasks, pid, comm);
 
 	return task;
 }
@@ -418,7 +422,7 @@ static void print_task_traces(struct perf_sched *sched)
 
 	for (i = 0; i < sched->nr_tasks; i++) {
 		task = sched->tasks[i];
-		printf("task %6ld (%20s:%10ld), nr_events: %ld\n",
+		printf("task %6ld (%20s:%10d), nr_events: %ld\n",
 			task->nr, task->comm, task->pid, task->nr_events);
 	}
 }
@@ -2981,6 +2985,12 @@ int cmd_sched(int argc, const char **argv, const char *prefix __maybe_unused)
 	};
 	unsigned int i;
 
+	sched.pid_to_task = intlist__new(NULL);
+	if (sched.pid_to_task == NULL) {
+		pr_err("Failed to allocate intlist for tracking tasks\n");
+		return -ENOMEM;
+	}
+
 	for (i = 0; i < ARRAY_SIZE(sched.curr_pid); i++)
 		sched.curr_pid[i] = -1;
 
-- 
2.3.0