linux-kernel - Re: tools/perf: "perf record" restricted to root in latest kernel?

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Message-ID: <20100106205911.GC18919@ghostprotocols.net>
Date:	Wed, 6 Jan 2010 18:59:11 -0200
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Miles Bader <miles@....org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: tools/perf: "perf record" restricted to root in latest kernel?

Em Wed, Jan 06, 2010 at 02:32:17PM +0900, Miles Bader escreveu:
> I tried compiling tools/perf in an old linux source tree (ab86e5765,
> roughly 2.6.31), and the resulting perf tool seemed to work fine
> ("perf record" ... "perf report", "perf stat" etc); I ran it as an
> ordinary user.
> 
> Next I updated to the latest linus tree (c5974b835a), and recompiled perf.
> It still seems to work, and has obviously had a lot of features added, but
> now it only wants to let me run "perf record" if I'm root.  This is
> slightly annoying -- even if I use "sudo" or make it setuid, it still ends
> up generating an output file owned by root, etc.
> 
> In both cases, I'm using the same kernel (I only recompiled the tool), 2.6.32.
> 
> I used no options with "perf record", just gave the command I wanted to profile.
> 
> Is there a reason why the newer version perf tool restricts "perf record"
> to root, especially given that the older version still seems to work fine
> as non-root?

Don't recall noticing such problem, here it works just fine:

[acme@...pio linux-2.6-tip]$ mkdir tmp
[acme@...pio linux-2.6-tip]$ cd tmp
[acme@...pio tmp]$ time perf record find ~/git/ > /dev/null
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.053 MB perf.data (~2312 samples) ]

real	0m25.602s
user	0m0.007s
sys	0m0.020s
[acme@...pio tmp]$ perf report | head -13
# Samples: 1628008142
#
# Overhead  Command           Shared Object  Symbol
# ........  .......  ......................  ......
#
     6.03%     find  libc-2.10.2.so          [.] _IO_vfprintf_internal
     5.70%     find  find                    [.] 0x0000000000351d
     3.39%     find  [kernel]                [k] ext4_htree_store_dirent
     2.85%     find  [kernel]                [k] __kmalloc
     2.14%     find  [kernel]                [k] _raw_spin_lock
     2.10%     find  [kernel]                [k] read_hpet
     2.10%     find  [kernel]                [k] half_md4_transform
     2.08%     find  libc-2.10.2.so          [.] __GI_memmove
[acme@...pio tmp]$ perf report --sort dso
# Samples: 1628008142
#
# Overhead                Shared Object
# ........  ...........................
#
    74.66%  [kernel]                   
    16.74%  libc-2.10.2.so             
     7.59%  find                       
     0.72%  ld-2.10.2.so               
     0.29%  libpthread-2.10.2.so       
[acme@...pio tmp]$ cd ..
[acme@...pio linux-2.6-tip]$ uname -r
2.6.33-rc3-tip+
[acme@...pio linux-2.6-tip]$ git branch | grep ^\*
* perf
[acme@...pio linux-2.6-tip]$ cat .git/refs/heads/perf
1dcff0bf19619e4d7bc61628770e6d88c631015c
[acme@...pio linux-2.6-tip]$

- Arnaldo
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