+==================
+Control Groupstats
+==================
+
Control Groupstats is inspired by the discussion at
http://lkml.org/lkml/2007/4/11/187 and implements per cgroup statistics as
suggested by Andrew Morton in http://lkml.org/lkml/2007/4/11/263.
information will not be available.
To extract cgroup statistics a utility very similar to getdelays.c
-has been developed, the sample output of the utility is shown below
+has been developed, the sample output of the utility is shown below::
-~/balbir/cgroupstats # ./getdelays -C "/sys/fs/cgroup/a"
-sleeping 1, blocked 0, running 1, stopped 0, uninterruptible 0
-~/balbir/cgroupstats # ./getdelays -C "/sys/fs/cgroup"
-sleeping 155, blocked 0, running 1, stopped 0, uninterruptible 2
+ ~/balbir/cgroupstats # ./getdelays -C "/sys/fs/cgroup/a"
+ sleeping 1, blocked 0, running 1, stopped 0, uninterruptible 0
+ ~/balbir/cgroupstats # ./getdelays -C "/sys/fs/cgroup"
+ sleeping 155, blocked 0, running 1, stopped 0, uninterruptible 2
+================
Delay accounting
-----------------
+================
Tasks encounter delays in execution when they wait
for some kernel resource to become available e.g. a
generic data structure to userspace corresponding to per-pid and per-tgid
statistics. The delay accounting functionality populates specific fields of
this structure. See
+
include/linux/taskstats.h
+
for a description of the fields pertaining to delay accounting.
It will generally be in the form of counters returning the cumulative
delay seen for cpu, sync block I/O, swapin, memory reclaim etc.
Usage
-----
-Compile the kernel with
+Compile the kernel with::
+
CONFIG_TASK_DELAY_ACCT=y
CONFIG_TASKSTATS=y
Delay accounting is enabled by default at boot up.
-To disable, add
+To disable, add::
+
nodelayacct
+
to the kernel boot options. The rest of the instructions
below assume this has not been done.
executed and the corresponding delays to be
seen.
-General format of the getdelays command
+General format of the getdelays command::
-getdelays [-t tgid] [-p pid] [-c cmd...]
+ getdelays [-t tgid] [-p pid] [-c cmd...]
-Get delays, since system boot, for pid 10
-# ./getdelays -p 10
-(output similar to next case)
+Get delays, since system boot, for pid 10::
-Get sum of delays, since system boot, for all pids with tgid 5
-# ./getdelays -t 5
+ # ./getdelays -p 10
+ (output similar to next case)
+Get sum of delays, since system boot, for all pids with tgid 5::
-CPU count real total virtual total delay total
- 7876 92005750 100000000 24001500
-IO count delay total
- 0 0
-SWAP count delay total
- 0 0
-RECLAIM count delay total
- 0 0
+ # ./getdelays -t 5
+
+
+ CPU count real total virtual total delay total
+ 7876 92005750 100000000 24001500
+ IO count delay total
+ 0 0
+ SWAP count delay total
+ 0 0
+ RECLAIM count delay total
+ 0 0
+
+Get delays seen in executing a given simple command::
-Get delays seen in executing a given simple command
-# ./getdelays -c ls /
+ # ./getdelays -c ls /
-bin data1 data3 data5 dev home media opt root srv sys usr
-boot data2 data4 data6 etc lib mnt proc sbin subdomain tmp var
+ bin data1 data3 data5 dev home media opt root srv sys usr
+ boot data2 data4 data6 etc lib mnt proc sbin subdomain tmp var
-CPU count real total virtual total delay total
+ CPU count real total virtual total delay total
6 4000250 4000000 0
-IO count delay total
+ IO count delay total
0 0
-SWAP count delay total
+ SWAP count delay total
0 0
-RECLAIM count delay total
+ RECLAIM count delay total
0 0
--- /dev/null
+:orphan:
+
+==========
+Accounting
+==========
+
+.. toctree::
+ :maxdepth: 1
+
+ cgroupstats
+ delay-accounting
+ psi
+ taskstats
+ taskstats-struct
Pressure information for each resource is exported through the
respective file in /proc/pressure/ -- cpu, memory, and io.
-The format for CPU is as such:
+The format for CPU is as such::
-some avg10=0.00 avg60=0.00 avg300=0.00 total=0
+ some avg10=0.00 avg60=0.00 avg300=0.00 total=0
-and for memory and IO:
+and for memory and IO::
-some avg10=0.00 avg60=0.00 avg300=0.00 total=0
-full avg10=0.00 avg60=0.00 avg300=0.00 total=0
+ some avg10=0.00 avg60=0.00 avg300=0.00 total=0
+ full avg10=0.00 avg60=0.00 avg300=0.00 total=0
The "some" line indicates the share of time in which at least some
tasks are stalled on a given resource.
/proc/pressure/ representing the resource to be monitored and write the
desired threshold and time window. The open file descriptor should be
used to wait for trigger events using select(), poll() or epoll().
-The following format is used:
+The following format is used::
-<some|full> <stall amount in us> <time window in us>
+ <some|full> <stall amount in us> <time window in us>
For example writing "some 150000 1000000" into /proc/pressure/memory
would add 150ms threshold for partial memory stall measured within
Userspace monitor usage example
===============================
-#include <errno.h>
-#include <fcntl.h>
-#include <stdio.h>
-#include <poll.h>
-#include <string.h>
-#include <unistd.h>
-
-/*
- * Monitor memory partial stall with 1s tracking window size
- * and 150ms threshold.
- */
-int main() {
+::
+
+ #include <errno.h>
+ #include <fcntl.h>
+ #include <stdio.h>
+ #include <poll.h>
+ #include <string.h>
+ #include <unistd.h>
+
+ /*
+ * Monitor memory partial stall with 1s tracking window size
+ * and 150ms threshold.
+ */
+ int main() {
const char trig[] = "some 150000 1000000";
struct pollfd fds;
int n;
}
return 0;
-}
+ }
Cgroup2 interface
=================
+====================
The struct taskstats
---------------------
+====================
This document contains an explanation of the struct taskstats fields.
the common fields and basic accounting fields are collected for
delivery at do_exit() of a task.
2) Delay accounting fields
- These fields are placed between
- /* Delay accounting fields start */
- and
- /* Delay accounting fields end */
+ These fields are placed between::
+
+ /* Delay accounting fields start */
+
+ and::
+
+ /* Delay accounting fields end */
+
Their values are collected if CONFIG_TASK_DELAY_ACCT is set.
3) Extended accounting fields
- These fields are placed between
- /* Extended accounting fields start */
- and
- /* Extended accounting fields end */
+ These fields are placed between::
+
+ /* Extended accounting fields start */
+
+ and::
+
+ /* Extended accounting fields end */
+
Their values are collected if CONFIG_TASK_XACCT is set.
4) Per-task and per-thread context switch count statistics
Future extension should add fields to the end of the taskstats struct, and
should not change the relative position of each field within the struct.
+::
-struct taskstats {
+ struct taskstats {
+
+1) Common and basic accounting fields::
-1) Common and basic accounting fields:
/* The version number of this struct. This field is always set to
* TAKSTATS_VERSION, which is defined in <linux/taskstats.h>.
* Each time the struct is changed, the value should be incremented.
*/
__u16 version;
- /* The exit code of a task. */
+ /* The exit code of a task. */
__u32 ac_exitcode; /* Exit status */
- /* The accounting flags of a task as defined in <linux/acct.h>
+ /* The accounting flags of a task as defined in <linux/acct.h>
* Defined values are AFORK, ASU, ACOMPAT, ACORE, and AXSIG.
*/
__u8 ac_flag; /* Record flags */
- /* The value of task_nice() of a task. */
+ /* The value of task_nice() of a task. */
__u8 ac_nice; /* task_nice */
- /* The name of the command that started this task. */
+ /* The name of the command that started this task. */
char ac_comm[TS_COMM_LEN]; /* Command name */
- /* The scheduling discipline as set in task->policy field. */
+ /* The scheduling discipline as set in task->policy field. */
__u8 ac_sched; /* Scheduling discipline */
__u8 ac_pad[3];
__u32 ac_pid; /* Process ID */
__u32 ac_ppid; /* Parent process ID */
- /* The time when a task begins, in [secs] since 1970. */
+ /* The time when a task begins, in [secs] since 1970. */
__u32 ac_btime; /* Begin time [sec since 1970] */
- /* The elapsed time of a task, in [usec]. */
+ /* The elapsed time of a task, in [usec]. */
__u64 ac_etime; /* Elapsed time [usec] */
- /* The user CPU time of a task, in [usec]. */
+ /* The user CPU time of a task, in [usec]. */
__u64 ac_utime; /* User CPU time [usec] */
- /* The system CPU time of a task, in [usec]. */
+ /* The system CPU time of a task, in [usec]. */
__u64 ac_stime; /* System CPU time [usec] */
- /* The minor page fault count of a task, as set in task->min_flt. */
+ /* The minor page fault count of a task, as set in task->min_flt. */
__u64 ac_minflt; /* Minor Page Fault Count */
/* The major page fault count of a task, as set in task->maj_flt. */
__u64 ac_majflt; /* Major Page Fault Count */
-2) Delay accounting fields:
+2) Delay accounting fields::
+
/* Delay accounting fields start
*
* All values, until the comment "Delay accounting fields end" are
/* version 1 ends here */
-3) Extended accounting fields
+3) Extended accounting fields::
+
/* Extended accounting fields start */
/* Accumulated RSS usage in duration of a task, in MBytes-usecs.
*/
__u64 coremem; /* accumulated RSS usage in MB-usec */
- /* Accumulated virtual memory usage in duration of a task.
+ /* Accumulated virtual memory usage in duration of a task.
* Same as acct_rss_mem1 above except that we keep track of VM usage.
*/
__u64 virtmem; /* accumulated VM usage in MB-usec */
- /* High watermark of RSS usage in duration of a task, in KBytes. */
+ /* High watermark of RSS usage in duration of a task, in KBytes. */
__u64 hiwater_rss; /* High-watermark of RSS usage */
- /* High watermark of VM usage in duration of a task, in KBytes. */
+ /* High watermark of VM usage in duration of a task, in KBytes. */
__u64 hiwater_vm; /* High-water virtual memory usage */
/* The following four fields are I/O statistics of a task. */
/* Extended accounting fields end */
-4) Per-task and per-thread statistics
+4) Per-task and per-thread statistics::
+
__u64 nvcsw; /* Context voluntary switch counter */
__u64 nivcsw; /* Context involuntary switch counter */
-5) Time accounting for SMT machines
+5) Time accounting for SMT machines::
+
__u64 ac_utimescaled; /* utime scaled on frequency etc */
__u64 ac_stimescaled; /* stime scaled on frequency etc */
__u64 cpu_scaled_run_real_total; /* scaled cpu_run_real_total */
-6) Extended delay accounting fields for memory reclaim
+6) Extended delay accounting fields for memory reclaim::
+
/* Delay waiting for memory reclaim */
__u64 freepages_count;
__u64 freepages_delay_total;
-}
+
+::
+
+ }
+=============================
Per-task statistics interface
------------------------------
+=============================
Taskstats is a netlink-based interface for sending per-task and
The data exchanged between user and kernel space is a netlink message belonging
to the NETLINK_GENERIC family and using the netlink attributes interface.
-The messages are in the format
+The messages are in the format::
+----------+- - -+-------------+-------------------+
| nlmsghdr | Pad | genlmsghdr | taskstats payload |
To avoid losing statistics, userspace should do one or more of the following:
- increase the receive buffer sizes for the netlink sockets opened by
-listeners to receive exit data.
+ listeners to receive exit data.
- create more listeners and reduce the number of cpus being listened to by
-each listener. In the extreme case, there could be one listener for each cpu.
-Users may also consider setting the cpu affinity of the listener to the subset
-of cpus to which it listens, especially if they are listening to just one cpu.
+ each listener. In the extreme case, there could be one listener for each cpu.
+ Users may also consider setting the cpu affinity of the listener to the subset
+ of cpus to which it listens, especially if they are listening to just one cpu.
Despite these measures, if the userspace receives ENOBUFS error messages
indicated overflow of receive buffers, it should take measures to handle the
loss of data.
-
-----
A read-only nested-key file which exists on non-root cgroups.
Shows pressure stall information for CPU. See
- Documentation/accounting/psi.txt for details.
+ Documentation/accounting/psi.rst for details.
Memory
A read-only nested-key file which exists on non-root cgroups.
Shows pressure stall information for memory. See
- Documentation/accounting/psi.txt for details.
+ Documentation/accounting/psi.rst for details.
Usage Guidelines
A read-only nested-key file which exists on non-root cgroups.
Shows pressure stall information for IO. See
- Documentation/accounting/psi.txt for details.
+ Documentation/accounting/psi.rst for details.
Writeback
have cpu.pressure, memory.pressure, and io.pressure files,
which aggregate pressure stalls for the grouped tasks only.
- For more details see Documentation/accounting/psi.txt.
+ For more details see Documentation/accounting/psi.rst.
Say N if unsure.
git.samba.org / sfrench / cifs-2.6.git / commitdiff