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

From: Arnaldo Carvalho de Melo
Date: Tue Mar 31 2015 - 16:25:37 EST

Em Tue, Mar 31, 2015 at 08:32:37AM -0600, David Ahern escreveu:
> 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.

Humm, we already have an rb_tree for each task, its called
machine->threads, and it has struct thread instances, that in turn have
a ->priv point, can't it be used here?

- Arnaldo

> >From 159dc732e0ad66d9151e93761bc9c685872e9fa4 Mon Sep 17 00:00:00 2001
> From: David Ahern <david.ahern@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> ---
> 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
>

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