lkml.org 
[lkml]   [2003]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] elapsed times wrap
From
Date
Hugh Dickins writes:
> On Sat, 22 Feb 2003, Kai Germaschewski wrote:
>> On Sat, 22 Feb 2003, Hugh Dickins wrote:

>>> Userspace shows huge elapsed time across jiffies wrap:
>>> with USER_HZ less then HZ, sys_times needs jiffies_64
>>> to calculate its retval.
>>
>> That makes me wonder, aren't all uses of
>> jiffies_to_clock_t() broken then?
>
> I believe you're right, but it's less obvious to me
> that the other uses really want fixing e.g. would we
> be happy to maintain utime,stime,cutime,cstime as
> 64-bit on a 32-bit machine?
>
>> Well, all which take an absolute time as an argument at least.
>
> Yes, it's much more important to fix those where userspace
> habitually takes the difference. That certainly applies
> to the return value from sys_times, but I don't see any
> other cases as clear (though userspace may have good reason
> to take the difference of any of them).
>
> Perhaps a procps expert can advise?

That depends on how much you care about the problems.
Some that come to mind:

The OOM killer will be more likely to kill the wrong process.
CPU usage stats will be worthless junk.

On a 4-way box, you can hit troubles with cutime after
just 2 weeks of usage.

Consider changing just cutime. It's the value most likely
to wrap. Plain utime would be the second priority.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:33    [W:0.020 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site