From: Glauber Costa <glommer@parallels.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-kernel@vger.kernel.org>, <xemul@parallels.com>,
<paul@paulmenage.org>, <lizf@cn.fujitsu.com>,
<daniel.lezcano@free.fr>, <jbottomley@parallels.com>
Subject: Re: [PATCH 6/9] Include idle and iowait fields in cpuacct
Date: Tue, 20 Sep 2011 10:29:01 -0300 [thread overview]
Message-ID: <4E78951D.1020901@parallels.com> (raw)
In-Reply-To: <1316523928.13664.12.camel@twins>
On 09/20/2011 10:05 AM, Peter Zijlstra wrote:
> On Tue, 2011-09-20 at 09:58 -0300, Glauber Costa wrote:
>> On 09/20/2011 09:58 AM, Peter Zijlstra wrote:
>>> On Tue, 2011-09-20 at 09:36 -0300, Glauber Costa wrote:
>>>> On 09/20/2011 06:21 AM, Peter Zijlstra wrote:
>>>>> On Wed, 2011-09-14 at 17:04 -0300, Glauber Costa wrote:
>>>>>> These are slightly different from the others though:
>>>>>> (note to reviewers: might be better to put those in a separate
>>>>>> array?)
>>>>>>
>>>>>> Since idle/iowait are a property of the system - by definition,
>>>>>> no process from any cgroup is running when the system is idle,
>>>>>> they are system wide. So what these fields really mean, are baselines
>>>>>> for when the cgroup was created. It allows the cgroup to start
>>>>>> counting idle/iowait from 0.
>>>>>
>>>>> Alternatively you can make iowait based on nr_uninterruptible per cgroup
>>>>> and count all ticks _this_ cgroup was idle.
>>>> You think?
>>>>
>>>> Humm,humm... maybe...
>>>> iowait can indeed be seen as a process group characteristic. I was
>>>> mainly concerned about overhead here, specially for the idle case:
>>>
>>> The overhead of accounting per cgroup nr_uninterruptible is the worst I
>>> think, that's in the sleep/wakeup paths.
>>>
>>>> If we are idle, there is no task context we can draw from, since the
>>>> task in the cpu is the idle task. So we end up having to touch all
>>>> cgroups... Or am I missing something?
>>>>
>>>> Sounds expensive.
>>>
>>> Count the total number of ticks on the cpu (I think we already have
>>> that) and subtract the number of ticks in this cgroup (I think we also
>>> already have that), which should yield: number of ticks not in this
>>> cgroup, aka number of ticks this cgroup was idle.
>> No , no... remember steal time.
>
> Of course I don't.. that's virt stuff, I repress that with all my might.
> But add or subtract steal ticks someplace and it doesn't come out right?
That's what I am here for...
But back to your answer:
>>> Count the total number of ticks on the cpu (I think we already have
>>> that) and subtract the number of ticks in this cgroup (I think we also
>>> already have that),
Not sure if we have ticks in this cgroup... anyway, it can be done. We
need a baseline for what was the tick situation when the cgroup started
anyway.
next prev parent reply other threads:[~2011-09-20 13:29 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-14 20:04 [PATCH 0/9] Per-cgroup /proc/stat Glauber Costa
2011-09-14 20:04 ` [PATCH 1/9] Remove parent field in cpuacct cgroup Glauber Costa
2011-09-19 16:03 ` Peter Zijlstra
2011-09-19 16:09 ` Glauber Costa
2011-09-19 16:19 ` Peter Zijlstra
2011-09-19 16:30 ` Glauber Costa
2011-09-19 16:39 ` Peter Zijlstra
2011-09-19 16:41 ` Glauber Costa
2011-09-19 18:40 ` Peter Zijlstra
2011-09-20 17:29 ` Srivatsa Vaddagiri
2011-09-22 15:11 ` Balbir Singh
2011-09-22 15:17 ` Peter Zijlstra
2011-09-23 8:09 ` Balbir Singh
2011-09-23 14:35 ` Peter Zijlstra
2011-09-23 15:45 ` Glauber Costa
2011-09-19 18:35 ` Peter Zijlstra
2011-09-19 18:38 ` Glauber Costa
2011-09-19 18:44 ` Peter Zijlstra
2011-09-19 19:14 ` Glauber Costa
2011-09-19 19:18 ` Peter Zijlstra
2011-09-19 19:19 ` Glauber Costa
2011-09-14 20:04 ` [PATCH 2/9] Make cpuacct fields per cpu variables Glauber Costa
2011-09-19 16:10 ` Peter Zijlstra
2011-09-14 20:04 ` [PATCH 3/9] Include nice values in cpuacct Glauber Costa
2011-09-19 16:19 ` Peter Zijlstra
2011-09-19 16:26 ` Glauber Costa
2011-09-19 18:36 ` Peter Zijlstra
2011-09-19 18:37 ` Glauber Costa
2011-09-14 20:04 ` [PATCH 4/9] Include irq and softirq fields " Glauber Costa
2011-09-19 18:38 ` Peter Zijlstra
2011-09-19 18:40 ` Glauber Costa
2011-09-14 20:04 ` [PATCH 5/9] Include guest " Glauber Costa
2011-09-14 20:04 ` [PATCH 6/9] Include idle and iowait " Glauber Costa
2011-09-20 9:21 ` Peter Zijlstra
2011-09-20 12:36 ` Glauber Costa
2011-09-20 12:58 ` Peter Zijlstra
2011-09-20 12:58 ` Glauber Costa
2011-09-20 13:05 ` Peter Zijlstra
2011-09-20 13:29 ` Glauber Costa [this message]
2011-09-14 20:04 ` [PATCH 7/9] Create cpuacct.proc.stat file Glauber Costa
2011-09-20 9:22 ` Peter Zijlstra
2011-09-20 12:22 ` Glauber Costa
2011-09-14 20:04 ` [PATCH 8/9] per-cgroup boot time Glauber Costa
2011-09-20 9:25 ` Peter Zijlstra
2011-09-20 12:37 ` Glauber Costa
2011-09-20 13:04 ` Peter Zijlstra
2011-09-20 13:06 ` Glauber Costa
2011-09-20 13:31 ` Peter Zijlstra
2011-09-14 20:04 ` [PATCH 9/9] Report steal time for cgroup Glauber Costa
2011-09-20 9:29 ` Peter Zijlstra
2011-09-14 20:13 ` [PATCH 0/9] Per-cgroup /proc/stat Peter Zijlstra
2011-09-14 20:20 ` Glauber Costa
2011-09-15 8:53 ` Peter Zijlstra
2011-09-14 20:23 ` Andi Kleen
2011-09-15 8:56 ` Peter Zijlstra
2011-09-19 23:07 ` Paul Turner
2011-09-20 8:33 ` Peter Zijlstra
2011-09-20 21:37 ` Glauber Costa
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