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

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Message-ID: <alpine.LRH.2.20.2407161424070.11376@Diego>
Date: Tue, 16 Jul 2024 14:29:49 +0200 (CEST)
From: Michael Petlan <mpetlan@...hat.com>
To: royenheart <royenheart@...il.com>
cc: Namhyung Kim <namhyung@...nel.org>, vmolnaro@...hat.com, 
    peterz@...radead.org, mingo@...hat.com, acme@...nel.org, 
    mark.rutland@....com, alexander.shishkin@...ux.intel.com, jolsa@...nel.org, 
    irogers@...gle.com, adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
    linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
    Yuan Tan <tanyuan@...ylab.org>
Subject: Re: [PATCH 1/1] perf archive: unpack to correct dir given by perf

On Tue, 16 Jul 2024, royenheart wrote:
> 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.
> > 
> >>

[...]

> 
> 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
> 

Shouldn't then perf-archive just determine the directory from perf-config
without any additional env var?

> 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.

As above, the var seems to be a duplicate to what is already stored in
perf-config...

> 
> 

Regards,
Michael