Hi,
Here is a sereis of patches for enabling "event cache" feature
to perf probe. Brendan gives me this cool idea, thanks! :)
In this series, I added following options/features;
- --output option
We can save the probe definition command for given probe-event
instead of setting up the local tracing/kprobe_events.
- --no-inlines option
We can avoid searching the inline functions in debuginfo. Usually
useful with wildcards since the wildcards will hit a huge amount
of probe-points.
- $params special probe argument
$params is expanded to function parameters only, no locally defined
variables. This is useful for function-call tracing.
- wildcard support for function name
Wildcard support is the key feature for this idea. Now we can use
'*foo*' for function name to define the probe-point.
So by using all of them, we can make an "event cache" file on all
functions (except for inlined functions) as below.
# perf probe --max-probes=100000 --no-inlines -a '* $params' -o event.cache
builds "event.cache" file in which event settings for
all function entries, like below;
p:probe/reset_early_page_tables _text+12980741
p:probe/copy_bootdata _text+12980830 real_mode_data=%di:u64
p:probe/exit_amd_microcode _text+14692680
p:probe/early_make_pgtable _text+12981274 address=%di:u64
p:probe/x86_64_start_reservations _text+12981700 real_mode_data=%di:u64
p:probe/x86_64_start_kernel _text+12981744 real_mode_data=%di:u64
p:probe/reserve_ebda_region _text+12982117
This event.cache file will be big (but much smaller than native
debuginfo :) ) if your kernel have many option embedded.
Anyway, you can compress it too.
# wc -l event.cache
33813 event.cache
# ls -sh event.cache
2.3M event.cache
# ls -sh event.cache.gz
464K event.cache.gz
For setting up a probe event, you can grep the function name
and write it to tracing/kprobe_events, as below;
# zcat event.cache.gz | \
grep probe/vfs_symlink > /sys/kernel/debug/tracing/kprobe_events
This can be applied for the remote machine only if the machine
runs on completely same kernel binary. Perhaps, we need some
helper tool to check it.
Thank you,
---
Masami Hiramatsu (6):
[BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no
instance
[DOC] perf-probe: Update perf-probe document
perf-probe: Add --output option to write commands in a standard file
perf-probe: Add --no-inlines option to avoid searching inline functions
perf-probe: Support $params special probe argument
perf-probe: Support glob wildcards for function name
tools/perf/Documentation/perf-probe.txt | 25 ++++++++++
tools/perf/builtin-probe.c | 32 +++++++++++++
tools/perf/util/dwarf-aux.c | 31 +++++++++++++
tools/perf/util/dwarf-aux.h | 6 +++
tools/perf/util/probe-event.c | 73 +++++++++++++++++++++++--------
tools/perf/util/probe-event.h | 4 +-
tools/perf/util/probe-finder.c | 74 +++++++++++++++++++------------
tools/perf/util/probe-finder.h | 6 ++-
tools/perf/util/util.h | 4 ++
9 files changed, 202 insertions(+), 53 deletions(-)
--
Masami HIRAMATSU
Software Platform Research Dpt. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu...@hitachi.com
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