Shailabh Nagar wrote:
Balbir Singh wrote:
Andrew Morton wrote:
per-task-delay-accounting-setup.patch
per-task-delay-accounting-setup-fix-1.patch
per-task-delay-accounting-setup-fix-2.patch
per-task-delay-accounting-sync-block-i-o-and-swapin-delay-collection.patch
per-task-delay-accounting-sync-block-i-o-and-swapin-delay-collection-fix-1.patch
per-task-delay-accounting-cpu-delay-collection-via-schedstats.patch
per-task-delay-accounting-cpu-delay-collection-via-schedstats-fix-1.patch
per-task-delay-accounting-utilities-for-genetlink-usage.patch
per-task-delay-accounting-taskstats-interface.patch
per-task-delay-accounting-taskstats-interface-fix-1.patch
per-task-delay-accounting-taskstats-interface-fix-2.patch
per-task-delay-accounting-delay-accounting-usage-of-taskstats-interface.patch
per-task-delay-accounting-delay-accounting-usage-of-taskstats-interface-use-portable-cputime-api-in-__delayacct_add_tsk.patch
per-task-delay-accounting-documentation.patch
per-task-delay-accounting-proc-export-of-aggregated-block-i-o-delays.patch
per-task-delay-accounting-proc-export-of-aggregated-block-i-o-delays-warning-fix.patch
I just don't know. There are a number of groups who pop up with various
enhanced accounting requirements and patches (all quite different) but I
haven't heard a lot of enthusiasm from any of them over this work, which
attempts to provide an extensible framework for accumulation and
querying
of per-task metrics.
But then again, we cannot just sit there and wait for everyone to be
100%
happy. So I'm 51% inclined to push this along.
Anyone else who has an interest in this sort of thing needs to be aware
that there will be an expectation that any future statistics submissions
should use these interfaces. So the time to pay attention is right now.
Hi, Andrew,
Here is a brief summary of the status of the response we have received from
the stakeholders (some of it has been duplicated in previous postings)
Project Response
1. CSA accounting/PAGG/JOB: Has agreed to use taskstats
Jay Lan <[email protected]> interface
2. per-process IO statistics: None
Levent Serinol <[email protected]> Needs are subset of CSA
3. per-cpu time statistics: None (email bounced)
Erich Focht <[email protected]> Needs can be met by taskstats
Statistics not yet submitted
4. Microstate accounting: None
Peter Chubb <[email protected]> overlap with delay accounting
prefers /proc due to
convenience
taskstats can meet the needs
5. ELSA: Guillaume Thouvenin None
<[email protected]> ELSA is not a direct user
of new kernel statistics
Consumer of CSA/BSD
accounting
statistics
6. pnotify: Jes Sorensen <[email protected]> None
(taken over pnotify from Erik Jacobson) Informed over private email
that pnotify replacement is
being worked on. pnotify
or its replacement will
not be concerned with
exporting data to user space
or collecting any statistics.
7. Scalable statistics counters with /proc Not working on it
reporting: anymore
Ravikiran G Thirumalai,
Dipankar Sarma <[email protected]>
Studying the responses from all stake holders, Jay Lan's was the most
encouraging. Peter Chubb prefers the /proc interface due to the text
interface
and ease of parsing. (in our opinion, taskstats can meet the needs easily
and the getdelays utility can provide the same ease for parsing).
The others did not respond.
Some performance numbers of taskstats were posted at
http://lkml.org/lkml/2006/3/23/141. The result highlights are included
below
Results highlights
- Configuring delay accounting adds < 0.5%
overhead in most cases and even reduces overhead
in some cases
- Enabling delay accounting has similar results
with a maximum overhead of 1.2% for hackbench,
most other overheads < 1% and reduction in
overhead in some cases
These statistics are _per task_ and can be extended easily by anyone
who wishes to obtain per task data. An example of per task improved
scheduler statistics was mentioned in http://lkml.org/lkml/2006/6/1/381
(I am not sure if the email refers to our per-task statistics). If not,
the new statistics could easily use the taskstats interface.
These statistics can be used by software product stacks to monitor
usage information about the various tasks they create and control.
I also informally spoke to a group of students (verbally), who were
excited at the possibility of using the per-task statistics to do
dynamic deadline based power management. They want to use the delay data
(CPU and IO) to predict deadlines for a task and then use these results
for dynamically scaling CPU frequency.
The ability to monitor the CPU run and delay data and IO delay data is
useful.
I would request you to consider the inclusion per-task delay accounting
into
2.6.18.
Andrew,
The only other new set of patches to be discussed in this context are the
statistics-infrastructure patches from Martin Peschke.
That infrastructure cannot meet the needs of delay accounting, CSA etc. because
- it only provides "user pull" model of getting stats whereas "kernel push" is
needed for delay accounting
Doesn't taskstats interface provide "user pull" request-reply model
also? Serious accounting needs to push accounting data as soon as
possible.
- it uses a relatively slow interface unsuitable for high volumes of data. Each
statistic has its own definition, needs to be read separately using ASCII,
reading data continuously means open/read/close each time.....all of
which is not very conducive to large structures being sent to userspace.
Yes, i second the point. It won't be able to catch up the traffic.
- its oriented towards sampled data whereas taskstats isn't.
So, we have a good consensus from existing/potential users of taskstats and would
very much appreciate it being included in 2.6.18.
Andrew, it has become clear that the community wants to see accounting
data processing being moved to userspace. Thus there is a need for a
common accounting interface to provide minimal works at kernel (via
hooks at fork and exit) and deliver data to userspace.
The delayacct patchset provides a good framework and example that
i believe CSA/Job can follow and build upon to move most of our work
to userspace and thus cut off dependency of PAGG. We will submit CSA
patch soon based on the taskstats interface.
Thanks,
- jay
P.S. Balbir and Shailabh, Chris Sturtivant will continue the CSA work
at SGI. Please also cc Chris <[email protected]> in the future.
Thanks!
--Shailabh
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