Re: [PATCH 1/1] perf archive: unpack to correct dir given by perf

[royenheart <royenheart@gmail.com>]

On 2024/7/12 12:35, Namhyung Kim wrote:
> Hello,
> 
> On Mon, Jul 08, 2024 at 02:04:31AM +0800, Haoze Xie wrote:
>> In perf-archive.sh, the code segment that defines 'PERF_BUILDID_DIR' is
>> advanced before 'unpack' operation for subsequent use, followed by a
>> 'mkdir' operation to ensure that the dir exists. Symbols in 'unpack' will
>> be extracted to correct dir given by perf.
>>
>> When '--unpack' param is appointed, the symbols are extracted to '~/.debug'
>> folder by default, without using 'PERF_BUILDID_DIR' given by perf. This
>> will cause perf to be unable to find the correct buildid's path when users
>> configured buildid.dir in 'perf config' or used '--buildid-dir' cli param,
>> since perf will read these params and put them in 'PERF_BUILDID_DIR' env.
>> 'perf script' and 'perf report' will use the env as the basis for buildid
>> indexing.
> 
> Can you please add an example command line and the output for the error
> case?  It'd be helpful to understand the problem more intuitively.
> 
>>
>> Fixes: e43c64c971e4 ("perf archive: Add new option '--unpack' to expand tarballs")
>> Signed-off-by: Haoze Xie <royenheart@gmail.com>
>> Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
>> ---
>>  tools/perf/perf-archive.sh | 28 +++++++++++++++-------------
>>  1 file changed, 15 insertions(+), 13 deletions(-)
>>
>> diff --git a/tools/perf/perf-archive.sh b/tools/perf/perf-archive.sh
>> index 6ed7e52ab881..f29bbc129056 100755
>> --- a/tools/perf/perf-archive.sh
>> +++ b/tools/perf/perf-archive.sh
>> @@ -23,6 +23,19 @@ while [ $# -gt 0 ] ; do
>>  	fi
>>  done
>>  
>> +#
>> +# PERF_BUILDID_DIR environment variable set by perf
>> +# path to buildid directory, default to $HOME/.debug
>> +#
>> +if [ -z $PERF_BUILDID_DIR ]; then
>> +	PERF_BUILDID_DIR=~/.debug/
>> +else
>> +	# append / to make substitutions work
>> +	PERF_BUILDID_DIR=$PERF_BUILDID_DIR/
>> +fi
>> +
>> +mkdir -p $PERF_BUILDID_DIR
>> +
>>  if [ $UNPACK -eq 1 ]; then
>>  	if [ ! -z "$UNPACK_TAR" ]; then					# tar given as an argument
>>  		if [ ! -e "$UNPACK_TAR" ]; then
>> @@ -65,25 +78,14 @@ if [ $UNPACK -eq 1 ]; then
>>  		fi
>>  
>>  		# unzip the perf.data file in the current working directory	and debug symbols in ~/.debug directory
>> -		tar xvf $TARGET && tar xvf $PERF_SYMBOLS.tar.bz2 -C ~/.debug
>> +		tar xvf $TARGET && tar xvf $PERF_SYMBOLS.tar.bz2 -C $PERF_BUILDID_DIR
>>  
>>  	else																# perf tar generated by perf archive (contains only debug symbols)
> 
> Off-topic.  I'm surprised by the comment placement.
> It'd be nice if you (or someone else) can update the whole file and
> remove the unnecessary whitespaces altogether.
> 
> Thanks,
> Namhyung
> 
> 
>> -		tar xvf $TARGET -C ~/.debug
>> +		tar xvf $TARGET -C $PERF_BUILDID_DIR
>>  	fi
>>  	exit 0
>>  fi
>>  
>> -#
>> -# PERF_BUILDID_DIR environment variable set by perf
>> -# path to buildid directory, default to $HOME/.debug
>> -#
>> -if [ -z $PERF_BUILDID_DIR ]; then
>> -	PERF_BUILDID_DIR=~/.debug/
>> -else
>> -        # append / to make substitutions work
>> -        PERF_BUILDID_DIR=$PERF_BUILDID_DIR/
>> -fi
>> -
>>  BUILDIDS=$(mktemp /tmp/perf-archive-buildids.XXXXXX)
>>  
>>  perf buildid-list -i $PERF_DATA --with-hits | grep -v "^ " > $BUILDIDS
>> -- 
>> 2.25.1
>>

I have two machines A and B, I use 'perf record' and 'perf archive' to get
a buildid archive 'perf.data.tar.bz2' on A: 

$ perf record -a -g -- sleep 1
$ perf archive

then I transfer 'perf.data' and its buildid archive to B. On machine B, I
use 'perf archive' to extract the buildid:

$ perf archive --unpack
$   Found target file for unpacking: ./perf.data.tar.bz2
$   .build-id/d1/a727ab038085dbbb50e74c812e5a6e8502e8c7
$   ...

But when I use 'perf script' to view hotspots, no function names are shown:

$ perf script
$   No kallsyms or vmlinux with build-id 
$   251c1248b97a17df394058a189dffe381169ddcd was found
$   perf    1770 [000] 1022235.467607:          1 cycles:P: 
$           ffffffff8ae9ceb6 [unknown] ([kernel.kallsyms])
$           ffffffff8ae15af5 [unknown] ([kernel.kallsyms])
$           ffffffff8ae0f83b [unknown] ([kernel.kallsyms])
$   ......

The problem is, I used 'perf config' to change buildid search path before:

$ perf config --user buildid.dir=/usr/local/symbols
$ cat ~/.perfconfig
$   # this file is auto-generated.
$   [buildid]
$           dir = /usr/local/symbols

But 'perf archive --unpack' just extract them to '~/.debug', which makes
perf can't found right path to search for buildid info. If I add
'buildid-dir' param to replace buildid path defined in perfconfig, problem
can be solved temporarily:

$ ./perf --buildid-dir ~/.debug script
$   perf    1770 [000] 1022235.467607:          1 cycles:P: 
$           ffffffff8ae9ceb6 native_write_msr+0x6 ([kernel.kallsyms])
$           ffffffff8ae15af5 intel_pmu_enable_all+0x15 ([kernel.kallsyms])
$           ffffffff8ae0f83b x86_pmu_enable+0x1ab ([kernel.kallsyms])

The code that determines the buildid path is in the 
'util/config.c:set_buildid_dir' function, which will generate
'PERF_BUILDID_DIR' var.