Re: [PATCH v2 3/4] perf-report: add --max-stack option to limit callchainstack scan
From: David Ahern
Date: Fri Oct 18 2013 - 13:30:57 EST
On 10/18/13 8:38 AM, Waiman Long wrote:
When callgraph data was included in the perf data file, it may take a
long time to scan all those data and merge them together especially
if the stored callchains are long and the perf data file itself is
large, like a Gbyte or so.
The callchain stack is currently limited to PERF_MAX_STACK_DEPTH (127).
This is a large value. Usually the callgraph data that developers are
most interested in are the first few levels, the rests are usually
not looked at.
This patch adds a new --max-stack option to perf-report to limit the
depth of callchain stack data to look at to reduce the time it takes
for perf-report to finish its processing. It trades the presence of
trailing stack information with faster speed.
The following table shows the elapsed time of doing perf-report on a
perf.data file of size 985,531,828 bytes.
--max_stack Elapsed Time Output data size
----------- ------------ ----------------
not set 88.0s 124,422,651
64 87.5s 116,303,213
32 87.2s 112,023,804
16 86.6s 94,326,380
8 59.9s 33,697,248
4 40.7s 10,116,637
-g none 27.1s 2,555,810
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
---
tools/perf/Documentation/perf-report.txt | 8 ++++++++
tools/perf/builtin-report.c | 22 +++++++++++++++++-----
tools/perf/builtin-top.c | 3 ++-
tools/perf/util/machine.c | 14 +++++++++-----
tools/perf/util/machine.h | 3 ++-
tools/perf/util/session.c | 3 ++-
6 files changed, 40 insertions(+), 13 deletions(-)
Looks good to me. Acked-by: David Ahern <dsahern@xxxxxxxxx>
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