(Long thread that was originally posted over here:
http://tinyurl.com/4akxa5 )
I've found that when running on battery (and the battery is not full)
the system will stall while battery information is read when using a non
preemptive kernel.
I can reliably hear the stalls at runlevel 1 by running
speaker-test -b75000
and
watch --interval=1 cat /proc/acpi/battery/BAT0/info
within separate terminals within screen.
I have ftraces of the stalls but the traces become large very quickly.
To that end I have disabled the tracing of certain functions to allow
part of the traces to be produced.
By doing counts across multiple runs I would say that the most
frequently called functions are the following (in most frequently called
order). The counts are definitely approximate but are reasonable
relative to each other.
475325 acpi_os_release_object (acpi_ut_delete_generic_state)
406895 kmem_cache_free (acpi_os_release_object)
402838 kmem_cache_alloc (acpi_ut_create_generic_state)
132968 acpi_ut_update_ref_count (acpi_ut_update_object_reference)
131041 acpi_ut_pop_generic_state (acpi_ut_update_object_reference)
131036 acpi_ut_delete_generic_state (acpi_ut_update_object_reference)
131025 acpi_ut_create_generic_state (acpi_ut_create_update_state)
131023 acpi_ut_create_update_state_and_push
(acpi_ut_update_object_reference)
131020 acpi_ut_create_update_state (acpi_ut_create_update_state_and_push)
131018 acpi_ut_push_generic_state (acpi_ut_create_update_state_and_push)
60147 acpi_ns_get_next_node (acpi_ns_delete_namespace_by_owner)
28974 acpi_ns_get_next_valid_node (acpi_ns_get_next_node)
Here's the command line I used to disable the tracing of certain
frequent functions:
echo acpi_os_release_object > set_ftrace_notrace && echo kmem_cache_* >>
set_ftrace_notrace && echo acpi_ut_* >> set_ftrace_notrace
Logs with the filtering on can be seen here (15Mbytes decompressed each):
http://sucs.org/~sits/test/eeepc-debug/20080923/latency_trace.gz
http://sucs.org/~sits/test/eeepc-debug/20080923/trace.txt.gz
I guess the aim is to find a good point to put cond_resched() or
otherwise solve the latency issue.
--
Sitsofe | http://sucs.org/~sits/
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