linux-kernel - Re: [RESEND][PATCH 0/4] Virtual Machine Time Accounting

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Message-ID: <46E64C9D.2000509@bull.net>
Date:	Tue, 11 Sep 2007 10:06:53 +0200
From:	Laurent Vivier <Laurent.Vivier@...l.net>
To:	Alistair John Strachan <alistair@...zero.co.uk>
Cc:	Avi Kivity <avi@...ranet.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND][PATCH 0/4] Virtual Machine Time Accounting

Alistair John Strachan wrote:
> On Monday 10 September 2007 14:08:45 Laurent Vivier wrote:
>> Avi Kivity wrote:
>>> Ingo Molnar wrote:
>>>> * Laurent Vivier <Laurent.Vivier@...l.net> wrote:
>>>>> Ingo, please, could you have a look to these patches ?
>>>>>
>>>>> The aim of these four patches is to introduce Virtual Machine time
>>>>> accounting.
>>>>>
>>>>> [PATCH 1/4] as recent CPUs introduce a third running state, after
>>>>> "user" and "system", we need a new field, "guest", in cpustat to
>>>>> store the time used by the CPU to run virtual CPU. Modify /proc/stat
>>>>> to display this new field.
>>>> the concept certainly looks sane to me.
>>>>
>>>> The heavy-handed use of #ifdefs uglifies the code to a large degree,
>>>> but this is not a fundamental problem: since basically all distros
>>>> have KVM enabled (and lguest benefits from this too), could you just
>>>> make all this new code unconditional?
>>> I imagine the embedded people will complain... perhaps move all the code
>>> to a #ifdef section above with a full implementation and a stub
>>> implementation.
>> I'm going to repost patches without #ifdefs for readability.
>> Then we could discuss if we should introduce #ifdefs and how.
> 
> If you could provide a summary of the size increase from your latest post 
> (i.e., size of the kernel before and after) that might lay rest to some 
> theoretical complaints.

These patches add:

* at data structures level:

- one cputime64_t (8 bytes) per cpu
- two cputime_t (2 * 4 bytes) per signal_struct and one cputime_t per task_struct

* at processing level:

- display and convert one more value in show_stat() (fs/proc/proc_misc.c)
- display and convert two more values in do_task_stat() (fs/proc/array.c)
- manage (copy and add) one more value in __exit_signal() (kernel/exit.c)
- initialize three more fields in copy_signal (kernel/fork.c)
- add a bit test in account_system_time() and if the bit is set call a new
function (46 bytes on x86_64).

Size of stripped kernel before (on x86_64):
vmlinux 7305064 bytes (not stripped 52643888 bytes)
Size of stripped kernel after:
vmlinux 7305064 bytes (not stripped 52677180 bytes)

means 0 bytes added ????

Laurent
-- 
------------- Laurent.Vivier@...l.net  --------------
          "Software is hard" - Donald Knuth


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