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Message-ID: <5523DA62.80208@huawei.com>
Date: Tue, 7 Apr 2015 21:23:46 +0800
From: Yunlong Song <yunlong.song@...wei.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
David Ahern <dsahern@...il.com>
CC: <a.p.zijlstra@...llo.nl>, <paulus@...ba.org>, <mingo@...hat.com>,
<linux-kernel@...r.kernel.org>, <wangnan0@...wei.com>
Subject: Re: [PATCH 3/9] perf sched replay: Alloc the memory of pid_to_task
dynamically to adapt to the unexpected change of pid_max
On 2015/4/1 15:06, Yunlong Song wrote:
> On 2015/3/31 23:56, Arnaldo Carvalho de Melo wrote:
>> Em Tue, Mar 31, 2015 at 08:32:37AM -0600, David Ahern escreveu:
>>> On 3/31/15 7:46 AM, Yunlong Song wrote:
>>>> - 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.
>>
>> Yunlong, can you please check/Ack this?
>>
>> - Arnaldo
>>
>>> >From 159dc732e0ad66d9151e93761bc9c685872e9fa4 Mon Sep 17 00:00:00 2001
>>> From: David Ahern <david.ahern@...cle.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@...cle.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
>>>
>>
>>
>> .
>>
>
> I have checked David's patch, the difference with my patch is that David's patch
> uses a rblist to sort and search the pid's task with a time complexity of O(log n),
> while my patch uses the array (same as the original design) dynamically created with
> a time complexity of O(1). For every simple, my patch does not need to traverse a
> list and has nothing to do with the total number of tasks. The maximum value of
> pid_max is PID_MAX_LIMIT, which equals to 4*1024*1024 in x86_64. Then for each simple,
> David's patch has to cost O(log 4*1024*1024) in searching a pid's task, vs O(1) of
> my patch. So I suggest to use array instead of rblist to solve this problem and save
> unnecessary waste of time.
>
> However, if you finally decide to take David's patch rather than my patch, please ignore
> the following 3 patches:
>
> [PATCH 2/9] perf sched replay: Increase the MAX_PID value to fix assertion failure problem
> [PATCH 3/9] perf sched replay: Alloc the memory of pid_to_task dynamically to adapt to the
> unexpected change of pid_max
> [PATCH 4/9] perf sched replay: Realloc the memory of pid_to_task stepwise to adapt to the
> different pid_max configurations
>
> The other 6 patches in these patch sets still need to be applied to make other improvements
> and bug fixes.
>
These bugs in 'perf sched replay' reproduce one after another in x86_64 (with many cores), and
really need urgent fix.
--
Thanks,
Yunlong Song
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