Bureaucrats, dave_user, Administrators
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→Comparison with the software-based method (ftrace)
In the ftrace-based solution, an increase in kernel size of approximately 15% (code) and 9% (data) is observed compared to the kernel without ftrace. During the execution of ftrace it’s also necessary to reserve additional memory for the ring buffer. The number of source files used in building the kernel increases by 18% when the ftrace framework is included. The weight of the instrumentation required by TRACE32, on the other hand, is practically negligible both in terms of code and data.
{| class="wikitable"
|+
! rowspan="3" |Measuring points (*)
! colspan="5" |Average duration
[us]
|-
! rowspan="2" |No ftrace
No TRACE32 instr.
(baseline)
! colspan="2" |No ftrace
With TRACE32 instr.
! colspan="2" |ftrace enabled
No TRACE32 instr.
|-
!Absolute
!Increment w.r.t. the baseline
!Absolute
!Increment w.r.t. the baseline
|-
|<code>mmc_start_request</code>
|6.950
|8.108
|1.158
|36.875
|29.925
|-
|<code>mmc_request_done</code>
|0.770
|1.364
|0.594
|63.031
|62.261
|}
(*) measuring points are the part of functions where the instrumentation is added.
The functions average duration analysis of eMMC accesses highlights the greater weight required by <code>ftrace</code>. The tests were performed under the following conditions.
==== Conclusion ====
