From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754711AbbCaNpI (ORCPT ); Tue, 31 Mar 2015 09:45:08 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:53889 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754030AbbCaNoM (ORCPT ); Tue, 31 Mar 2015 09:44:12 -0400 From: Yunlong Song To: , , , CC: , Subject: [PATCH 3/9] perf sched replay: Alloc the memory of pid_to_task dynamically to adapt to the unexpected change of pid_max Date: Tue, 31 Mar 2015 21:46:30 +0800 Message-ID: <1427809596-29559-4-git-send-email-yunlong.song@huawei.com> X-Mailer: git-send-email 1.8.4.5 In-Reply-To: <1427809596-29559-1-git-send-email-yunlong.song@huawei.com> References: <1427809596-29559-1-git-send-email-yunlong.song@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.110.52.30] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current memory allocation of struct task_desc *pid_to_task[MAX_PID] is in a permanent and preset way, and it has two problems: Problem 1: If the pid_max, which is the max number of pids in the system, is much smaller than MAX_PID (1024*1000), then it causes a waste of stack memory. This may happen in the case where the number of cpu cores is much smaller than 1000. Problem 2: If the pid_max is changed from the default value to a value larger than MAX_PID, then it will cause assertion failure problem. The maximum value of pid_max can be set to pid_max_max (see pidmap_init defined in kernel/pid.c), which equals to PID_MAX_LIMIT. In x86_64, PID_MAX_LIMIT is 4*1024*1024 (defined in include/linux/threads.h). This value is much larger than MAX_PID, and will take up 32768 Kbytes (4*1024*1024*8/1024) for memory allocation of pid_to_task, which is much larger than the default 8192 Kbytes of the stack size of calling process. Due to these two problems, we use calloc to allocate the memory of pid_to_task dynamically. Example: Test environment: x86_64 with 160 cores $ cat /proc/sys/kernel/pid_max 163840 $ echo 1025000 > /proc/sys/kernel/pid_max $ cat /proc/sys/kernel/pid_max 1025000 Run some applications until the pid of some process is greater than the value of MAX_PID (1024*1000). Before this patch: $ perf sched replay run measurement overhead: 221 nsecs sleep measurement overhead: 55480 nsecs the run test took 1000008 nsecs the sleep test took 1063151 nsecs perf: builtin-sched.c:330: register_pid: Assertion `!(pid >= 1024000)' failed. Aborted After this patch: $ perf sched replay run measurement overhead: 221 nsecs sleep measurement overhead: 55435 nsecs the run test took 1000004 nsecs the sleep test took 1059312 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 --- tools/perf/builtin-sched.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) 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 #include #include +#include #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); task = sched->pid_to_task[pid]; -- 1.8.5.2