Profiling¶
What is profiling¶
Profiling, by its definition (see this wikipedia article for a non formal introduction), is to run an analysis tool to inspect the behavior of a certain property of the system (be it memory, CPU consumption or any other).
How autotest can help with profiling?¶
Autotest provides support for running profilers during the execution of
tests, so we know more about a given system resource. For the kvm
test, our first idea of profiling usage was to run the kvm_stat
program, that usually ships with kvm, to provide data useful for
debugging. kvm_stat provides the number of relevant kvm events every
time it is called, so by the end of a virt-test test we end up with a
long list of information like this one:
kvm_ack_i kvm_age_p kvm_apic kvm_apic_ kvm_apic_ kvm_async kvm_async kvm_async kvm_async kvm_cpuid kvm_cr kvm_emula kvm_entry kvm_exit kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_exit( kvm_fpu kvm_hv_hy kvm_hyper kvm_inj_e kvm_inj_v kvm_invlp kvm_ioapi kvm_mmio kvm_msi_s kvm_msr kvm_neste kvm_neste kvm_neste kvm_neste kvm_neste kvm_page_ kvm_pic_s kvm_pio kvm_set_i kvm_skini kvm_try_a kvm_users
1 54 11 5 0 0 0 0 0 0 3 15 28 28 11 0 3 0 0 0 1 2 5 0 0 5 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 5 0 2 11 0 0 0 0 0 0 0 0 2 5 2 0 0 5
How to control the execution of profilers ?¶
Profiling in virt-test is controlled through configuration files. You
can set the profilers that are going to run by setting the variable
profilers. On tests_base.cfg.sample, the section of the file
that sets the profilers that run by default looks like this:
# Profilers. You can add more autotest profilers (see list on client/profilers)
# to the line below. You can also choose to remove all profilers so no profiling
# will be done at all.
profilers = kvm_stat
How to add a profiler?¶
So, say you want to run the perf profiler in addition to kvm_stat. You can just edit that place and put ‘perf’ right next to it:
# Profilers. You can add more autotest profilers (see list on client/profilers)
# to the line below. You can also choose to remove all profilers so no profiling
# will be done at all.
profilers = kvm_stat perf
How to remove all profilers (including kvm_stat)?¶
If you want no profiling at all for your tests, profilers can be changed to be an empty string:
# Profilers. You can add more autotest profilers (see list on client/profilers)
# to the line below. You can also choose to remove all profilers so no profiling
# will be done at all.
profilers =
Of course, the config system makes it easy to override the value of any param for your test variable, so you can have fine grained control of things. Say you don’t want to run profilers on your new ‘crazy_test’ variant, which you have developed. Easy:
- crazy_test:
type = crazy_test
profilers =
So this will turn of profilers just for this particular test of yours.