Re: [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1
- From: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
- Date: Wed, 11 Mar 2009 22:14:16 +0530
* Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> [2009-03-11 20:46:57]:
* Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx> [2009-03-10 18:12:08]:
Hi,
Based on the comments received during my last post
(http://lkml.org/lkml/2009/2/25/129), here is a fresh attempt
to get per-cgroup utime/stime statistics as part of cpuacct controller.
This patch adds a new file cpuacct.stat which displays two stats:
utime and stime. I wasn't too sure about the usefulness of providing
per-cgroup guest and steal times and hence not including them here.
Note that I am using percpu_counter for collecting these two stats.
Since percpu_counter subsystem doesn't protect the readside, readers could
theoritically obtain incorrect values for these stats on 32bit systems.
I hope occasional wrong values is not too much of a concern for
statistics like this. If it is a problem, we have to either fix
percpu_counter or do it all by ourselves as Kamezawa attempted
for cpuacct.usage (http://lkml.org/lkml/2009/3/4/14)
Regards,
Bharata.
cpuacct: Add stime and utime statistics
Add per-cgroup cpuacct controller statistics like the system and user
time consumed by the group of tasks.
Signed-off-by: Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Balaji Rao <balajirrao@xxxxxxxxx>
---
Documentation/cgroups/cpuacct.txt | 8 +++
kernel/sched.c | 87 +++++++++++++++++++++++++++++++++++---
2 files changed, 89 insertions(+), 6 deletions(-)
--- a/Documentation/cgroups/cpuacct.txt
+++ b/Documentation/cgroups/cpuacct.txt
@@ -30,3 +30,11 @@ The above steps create a new group g1 an
process (bash) into it. CPU time consumed by this bash and its children
can be obtained from g1/cpuacct.usage and the same is accumulated in
/cgroups/cpuacct.usage also.
+
+cpuacct.stat file lists a few statistics which further divide the
+CPU time obtained by the cgroup into user and system times. Currently
+the following statistics are supported:
+
+utime: Time in milliseconds spent by tasks of the cgroup in user mode.
+stime: Time in milliseconds spent by tasks of the cgroup in kernel mode.
+
Hi, Bharata,
I did a quick run of the patch on my machine. The patch applied and
compile cleanly, here are a few comments?
1. We could consider enhancing the patch to account for irq, softirq,
etc time like cpustat does. Not right away, but iteratively
2. The accounting is converted to milliseconds, I would much rather
export it in cputime to be consistent with other cpu accounting.
I remember we used to return nanosecond accurate accounting and then
moved to cputime based accounting for cpuacct.
3. How do we deal with CPU hotplug. Since we use a per-cpu counter,
any hotplug would mean that the data related to the offlined CPU is
lost. That is how the current CPU accounting system seems to work.
Bharata,
I tried the diff below and saw what I was looking for
diff --git a/kernel/sched.c b/kernel/sched.c
index 015155d..fadd17f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4195,7 +4195,7 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
else
cpustat->user = cputime64_add(cpustat->user, tmp);
- cpuacct_update_stats(p, CPUACCT_STAT_UTIME, cputime_to_msecs(cputime));
+ cpuacct_update_stats(p, CPUACCT_STAT_UTIME, cputime);
/* Account for user time used */
acct_update_integrals(p);
}
@@ -4257,7 +4257,7 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
else
cpustat->system = cputime64_add(cpustat->system, tmp);
- cpuacct_update_stats(p, CPUACCT_STAT_STIME, cputime_to_msecs(cputime));
+ cpuacct_update_stats(p, CPUACCT_STAT_STIME, cputime);
/* Account for system time used */
acct_update_integrals(p);
@@ -9611,6 +9611,7 @@ static int cpuacct_stats_show(struct cgroup *cgrp, struct cftype *cft,
for (i = 0; i < CPUACCT_STAT_NSTATS; i++) {
s64 val = percpu_counter_read(&ca->cpustat[i]);
val *= cpuacct_stat_desc[i].unit;
+ val = cputime_to_clock_t(val);
cb->fill(cb, cpuacct_stat_desc[i].msg, val);
}
return 0;
1. The data is returned in clock_t
2. CPU hotplug seems to be already correctly handled by per_cpu
counters
--
Balbir
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- References:
- [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1
- From: Bharata B Rao
- Re: [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1
- From: Balbir Singh
- [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1
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