如何查看`ps`输出以外的进程调度策略

Question

我使用的是busybox版本的linux，想要检查进程调度策略。

PS

输出仅显示

PID USER       VSZ STAT COMMAND

，无论

PS

命令给出的任何选项如何。还有其他方法可以查看进程调度策略吗？

提前致谢！

Answer 1

您可以通过查看

/proc/pocess_id/sched

找到流程的调度信息。

例如：

awk '/policy/ {print $NF}' /proc/25/sched

会给你处理的保单编号

25

。

有关保单号码的更多信息，您可以查看

man sched_setscheduler

：

Scheduling Policies:
    ...
   For  threads scheduled under one of the normal scheduling policies
   (SCHED_OTHER, SCHED_IDLE, SCHED_BATCH), sched_priority is not used
   in scheduling decisions (it must be specified as 0).

   Processes scheduled under one of the real-time policies
   (SCHED_FIFO, SCHED_RR) have a sched_priority value in the range 1
   (low)  to  99  (high).  (As the numbers imply, real-time threads
   always have higher priority than normal threads.)  Note well:
   POSIX.1-2001 requires an implementation to support only a minimum
   32 distinct priority levels for the real-time policies, and some
   systems supply  just  this  minimum.   Portable  programs should
   use sched_get_priority_min(2) and sched_get_priority_max(2) to
   find the range of priorities supported for a particular policy.

Answer 2

如果您的 BusyBox 安装包含

chrt

，请获取例如PID 4242：

chrt -p 4242
# prints:
pid 4242s current scheduling policy: SCHED_OTHER
pid 4242s current scheduling priority: 0

如果您的 BusyBox 缺少

chrt

，您将不得不退回到 proc 文件系统。在我的嵌入式设备上，缺少

/proc/PID/sched

，但存在

/proc/PID/stat

。 使用

cut

获取策略值，该值位于字段 41：

cat /proc/4242/stat | cut -d ' ' -f 41
# prints:
0

0

表示 SCHED_NORMAL，请参阅

include/uapi/linux/sched.h

:

#define SCHED_NORMAL            0
#define SCHED_FIFO              1
#define SCHED_RR                2
#define SCHED_BATCH             3

stat

文件包含许多有趣的字段，例如nice value (19)、rt_priority (40) 和policy (41)。检查

man 5 proc

了解所有值。

 /proc/pid/stat
              Status information about the process.  This is used by
              ps(1).  It is defined in the kernel source file
              fs/proc/array.c.
[...]
              (40) rt_priority  %u  (since Linux 2.5.19)
                     Real-time scheduling priority, a number in the
                     range 1 to 99 for processes scheduled under a real-
                     time policy, or 0, for non-real-time processes (see
                     sched_setscheduler(2)).

              (41) policy  %u  (since Linux 2.5.19)
                     Scheduling policy (see sched_setscheduler(2)).
                     Decode using the SCHED_* constants in
                     linux/sched.h.

Answer 3

要了解您的内核配置了哪个 IO 调度程序，请输入：

cat /proc/config.gz |grep CONFIG_DEFAULT_IOSCHED