[Patch 0/8] per-task delay accounting

From: Shailabh Nagar
Date: Wed Mar 29 2006 - 19:29:53 EST


Could you please include the following delay accounting patches
in -mm ?

The patches have gone through several iterations on lkml and
numerous comments raised by reviewers have been addressed

- several netlink interface comments (Jamal)
- block I/O collection method (Arjan)
- block I/O delays export through /proc (Andi)
- performance issues (Greg) (just addressed, see below)
- GPL headers (Arjan)

Most of the descriptions of the patches are either in the
patch itself or in the documentation patch at the end.


Patch series


Results highlights

- No statistically significant performance degradation is seen in
kernbench, hackbench and large OLTP benchmark when delay
accounting is configured.

The overheads of configuring delay accounting,
without enabling at boot time, are statistically negligible
for hackbench and a large OLTP benchmark and negative
(i.e. performance improves) in kernbench.

- Similar lack of degradation is seen in kernbench and hackbench
even when delay accounting is enabled at boot.

No data could be collected for the large OLTP benchmark (efforts


Vanilla 2.6.16 kernel
without any patches applied
Delay accounting configured
but not enabled at boot
Delay accounting enabled at boot
but no stats read

Time Elapsed time, averaged over 10 runs
Stddev Standard deviation of elapsed times
Ovhd % difference of elapsed time with respect to base kernel
t-value Used to measure statistical significance
of difference of two mean values (in this
case mean elapsed time). Low t-values indicate
insignificant difference. The t-values here were
calculated at 95% confidence interval using the tool at

200 groups, using pipes
Elapsed time, in seconds, lower better

Ovhd Time Stddev Ovhd significant (t-value)
Base 0% 43.483 0.178 na
+patch 0.1% 43.517 0.265 No (0.337)
+patch+enable 0.3% 43.629 0.167 No (1.892)

Average of 10 iterations
Elapsed time, in seconds, lower better

Ovhd Time Stddev Ovhd significant (t-value)
Base 0% 196.704 0.459 na
+patch -0.5% 195.812 0.477 Yes (4.261)
+patch+enable 0.02% 196.752 0.356 No (0.261)

Large OLTP benchmark
An industry standard large database online transaction processing
workload was run with delay accounting patches configured
ON and OFF.

The performance degradation of delay accounting was about 0.2%,
which was well within the normal range of variation between
similar runs.

No runs were taken with delay accounting enabled at boot time.
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