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[REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly

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  [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly Martin Steigerwald <martin.steigerwald@teamix.de> - 2016-12-19 13:20 +0100
    Re: [REGRESSION] Two issues that prevent process accounting  (taskstats) from working correctly Peter Zijlstra <peterz@infradead.org> - 2016-12-19 14:20 +0100
      Re: [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly Martin Steigerwald <martin@lichtvoll.de> - 2016-12-19 15:00 +0100
        Re: [REGRESSION] Two issues that prevent process accounting  (taskstats) from working correctly Peter Zijlstra <peterz@infradead.org> - 2016-12-19 15:10 +0100
    Re: [REGRESSION] Two issues that prevent process accounting  (taskstats) from working correctly Peter Zijlstra <peterz@infradead.org> - 2016-12-19 18:30 +0100

#1544498 — [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly

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Hello Ingo, Peter, Nicolas, Andrew, Balbir, Shailabh, Jay, Gerlof and Marc,

starting from a Debian bug report of mine, Gerlof Langeveld, developer of 
system and process monitor atop¹, found two issues with process accounting.

[1] http://atoptool.nl/


I did some guess work on who might be the maintainer for this, but please feel 
free to add further Cc´s as you see fit. Or ask for removal for Cc if you are 
not working on this anymore.

Gerlof found two issues which I also reported to the kernel bug tracker. I 
copy and paste the summaries that Gerlof prepared:


1) Sometimes process accounting does not work at all.

The acct() system call (to activate process accounting) return value 0, 
which means that process accounting is activated successfully.
However, no process accounting records are written whatsoever. This 
situation can be reproduced with the program 'acctdemo.c'
that you can find as attachment. When this program gives the message 
"found a process accounting record!", the situation is okay
and process accounting works fine to the file '/tmp/mypacct'. When the 
message 'No process accounting record yet....' is repeatedly given,
process accounting does not work and will not work at all. It might be 
that you have to start this program several times before you get
this situation (preferably start/finish lots of processes in the mean time).
This problem is probably caused by a new mechanism introduced in the 
kernel code (..../linux/kernel/acct.c) that is called 'slow accounting'
and has to be solved in the kernel code.

I experience this problem on Debian8 with a 4.8 kernel and on CentOS7 
with a 4.8 kernel.

I reported this as:

Bug 190271 - process accounting sometimes does not work 
https://bugzilla.kernel.org/show_bug.cgi?id=190271



2) When using the NETLINK inface, the command TASKSTATS_CMD_GET 
consequently returns -EINVAL.

The code that is used by the atopacctd daemon is based on the demo code 
'getdelays.c' that can be found in the kernel source code tree
(..../linux/Documentation/accounting/getdelays.c). Also this 'getdelays' 
program does not work any more (also -EINVAL on the same call)
with the newer kernels. I really spent a lot of time on this issue to 
get the code running (there are many places in the kernel code where
-EINVAL for this call can be given), but I did not succeed. It is really 
an incompatibility introduced by the kernel code.
It would be nice if the kernel maintainers provide a working version of 
the getdelays program in the kernel source tree.

I only experience this problem on Debian8 with a 4.8 kernel (virtual 
machine with 4 cores).
On CentOS7 with a 4.8 kernel it works fine (physical machine with 4 cores).

I will anyhow adapt atopacctd for this issue that it detects and logs 
the -EINVAL and terminates.
The current version of atopacctd keeps running which is not useful at all.


I reported this as:

Bug 190711 - Process accounting: Using the NETLINK inface, the command 
TASKSTATS_CMD_GET returns -EINVAL

https://bugzilla.kernel.org/show_bug.cgi?id=190711


Marc Haber, maintainer of atop package, Gerlof Langeveld, developer of atop 
and I are currently discussing workarounds with atop and/or systemd service 
fail for the time till upstream kernels with this issues fixed are shipped by 
distributions. Still it would be nice to remove those work-arounds and have 
the kernel work correctly again at some time in the future.

Thanks,
-- 
Martin Steigerwald  | Trainer

teamix GmbH
Südwestpark 43
90449 Nürnberg

Tel.:  +49 911 30999 55 | Fax: +49 911 30999 99
mail: martin.steigerwald@teamix.de | web:  http://www.teamix.de | blog: http://blog.teamix.de

Amtsgericht Nürnberg, HRB 18320 | Geschäftsführer: Oliver Kügow, Richard Müller

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#1544522 — Re: [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly

On Mon, Dec 19, 2016 at 01:06:00PM +0100, Martin Steigerwald wrote:
> Hello Ingo, Peter, Nicolas, Andrew, Balbir, Shailabh, Jay, Gerlof and Marc,
> 
> starting from a Debian bug report of mine, Gerlof Langeveld, developer of 
> system and process monitor atop¹, found two issues with process accounting.
> 

While $subject says regression the rest of the email completely fails to
mentions if this ever worked, and if so, against what version.

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#1544541

Am Montag, 19. Dezember 2016, 14:19:11 CET schrieb Peter Zijlstra:
> On Mon, Dec 19, 2016 at 01:06:00PM +0100, Martin Steigerwald wrote:
> > Hello Ingo, Peter, Nicolas, Andrew, Balbir, Shailabh, Jay, Gerlof and
> > Marc,
> > 
> > starting from a Debian bug report of mine, Gerlof Langeveld, developer of
> > system and process monitor atop¹, found two issues with process
> > accounting.
> 
> While $subject says regression the rest of the email completely fails to
> mentions if this ever worked, and if so, against what version.

Sorry for not mentioning it here. With kernel 3.16 process accounting worked 
nicely. We do not have any data on the exact kernel version where it started 
to fail. I do see these issues since quite a while, but I was never sure 
whether it was an issue in atop or the kernel and I do not recall on what 
exact combination of atop + kernel version it failed to work.

As an additional notice: The mail addresses of Balbir and Shailabh which I got 
from source code annotations of taskstats.c and getdelays.c do not work 
anymore.

-- 
Martin

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#1544546 — Re: [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly

On Mon, Dec 19, 2016 at 02:50:25PM +0100, Martin Steigerwald wrote:
> Am Montag, 19. Dezember 2016, 14:19:11 CET schrieb Peter Zijlstra:
> > On Mon, Dec 19, 2016 at 01:06:00PM +0100, Martin Steigerwald wrote:
> > > Hello Ingo, Peter, Nicolas, Andrew, Balbir, Shailabh, Jay, Gerlof and
> > > Marc,
> > > 
> > > starting from a Debian bug report of mine, Gerlof Langeveld, developer of
> > > system and process monitor atop¹, found two issues with process
> > > accounting.
> > 
> > While $subject says regression the rest of the email completely fails to
> > mentions if this ever worked, and if so, against what version.
> 
> Sorry for not mentioning it here. With kernel 3.16 process accounting worked 
> nicely. We do not have any data on the exact kernel version where it started 
> to fail. I do see these issues since quite a while, but I was never sure 
> whether it was an issue in atop or the kernel and I do not recall on what 
> exact combination of atop + kernel version it failed to work.
> 
> As an additional notice: The mail addresses of Balbir and Shailabh which I got 
> from source code annotations of taskstats.c and getdelays.c do not work 
> anymore.

Right, Balbir is back with IBM and working on Linux again, but under a
different email address (and on a different continent). I've amended
his address and bounced him the initial email.

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#1544697 — Re: [REGRESSION] Two issues that prevent process accounting (taskstats) from working correctly

On Mon, Dec 19, 2016 at 01:06:00PM +0100, Martin Steigerwald wrote:
> 
> 2) When using the NETLINK inface, the command TASKSTATS_CMD_GET 
> consequently returns -EINVAL.
> 
> The code that is used by the atopacctd daemon is based on the demo code 
> 'getdelays.c' that can be found in the kernel source code tree
> (..../linux/Documentation/accounting/getdelays.c). Also this 'getdelays' 
> program does not work any more (also -EINVAL on the same call)
> with the newer kernels. I really spent a lot of time on this issue to 
> get the code running (there are many places in the kernel code where
> -EINVAL for this call can be given), but I did not succeed. It is really 
> an incompatibility introduced by the kernel code.
> It would be nice if the kernel maintainers provide a working version of 
> the getdelays program in the kernel source tree.
> 
> I only experience this problem on Debian8 with a 4.8 kernel (virtual 
> machine with 4 cores).
> On CentOS7 with a 4.8 kernel it works fine (physical machine with 4 cores).
> 
> I will anyhow adapt atopacctd for this issue that it detects and logs 
> the -EINVAL and terminates.
> The current version of atopacctd keeps running which is not useful at all.
> 
> 
> I reported this as:
> 
> Bug 190711 - Process accounting: Using the NETLINK inface, the command 
> TASKSTATS_CMD_GET returns -EINVAL
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=190711


Ben Hutchings reports:

"It looks like the taskstats bug was introduced by 513e3d2d11c9 as that
means cpumask_parse() may not initialise as many bits as
cpumask_subset() compares"

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