RE: failed to dump symbol info from opreport on MIPS

[Jian P. <ji...@br...>]

Hi, Maynard,

Here is the root cause

# echo 0 > /dev/oprofile/backtrace_depth
-sh: echo: write error: Invalid argument
#
#
# cat /dev/oprofile/backtrace_depth
0
#
# ls -lt /dev/oprofile/backtrace_depth
-rw-r--r--    1 root     root             0 Jan  1 01:05 /dev/oprofile/backtrace_depth
# mount | grep oprofile
nodev on /dev/oprofile type oprofilefs (rw,relatime)

I found a related post http://old.nabble.com/-usr-bin-opcontrol:-line-1016:-echo:-write-error:-Invalid-argument-td25897517.html, and will debug our oprofile driver.

Since the default value is 0 already, does this failure really matter?

Thanks,
Jian



-----Original Message-----
From: Maynard Johnson [mailto:may...@us...] 
Sent: Tuesday, April 19, 2011 2:16 PM
To: Jian Peng
Cc: opr...@li...
Subject: Re: failed to dump symbol info from opreport on MIPS

Jian Peng wrote:
> I am running Linux 2.6.31 and enabled Oprofile support in kernel image, and run simple testing as follow,
> 
> # opcontrol --init
> #
> # opcontrol --vmlinux=/root/vmlinux-initrd-7468b0-opf
> #
> # opcontrol --separate=kernel
> #
> # opcontrol --event=CYCLES:5000
> #
> # opcontrol --status
> Daemon not running
> Event 0: CYCLES:5000:0:1:1
> Separate options: library kernel
> vmlinux file: /root/vmlinux-initrd-7468b0-opf
> Image filter: none
> Call-graph depth: 0
> #

You should add 'opcontrol --reset' before starting to clear out old profile data.

> #
> # opcontrol --start
> /bin/opcontrol: line 1081: echo: write error: Invalid argument

This is bad-ness.  This error implies that oprofile isn't working properly, and you need to do some debugging.  What's on line 1081 of your opcontrol script?  Do you see any nasty messages in dmesg?

> Using 2.6+ OProfile kernel interface.
> Reading module info.
> Using log file /var/lib/oprofile/samples/oprofiled.log
> Daemon started.
> Profiler running.
> #
> #
> # opcontrol --stop
> Stopping profiling.
> #
> #
> # opreport --symbols
> Overflow stats not available
> warning: /bin/bash could not be found.
> warning: /bin/busybox could not be found.
> warning: /bin/ophelp could not be found.
> warning: /bin/oprofiled could not be found.
> warning: /lib/ld-uClibc-0.9.29.so could not be found.
> warning: /lib/libdl-0.9.29.so could not be found.
> warning: /lib/libgcc_s.so.1 could not be found.
> warning: /lib/libuClibc-0.9.29.so could not be found.
> warning: /root/vmlinux-initrd-7468b0-opf could not be found.
> CPU: Broadcom BMIPS3300, speed 405 MHz (estimated)
> Counted CYCLES events (Processor cycles (PClock)) with a unit mask of 0x00 (No unit mask) count 5000
> samples  %        image name               app name                 symbol name
> 389217   62.4515  vmlinux-initrd-7468b0-opf vmlinux-initrd-7468b0-opf /root/vmlinux-initrd-7468b0-opf
> 159935   25.6622  oprofiled                oprofiled                /bin/oprofiled
> 18333     2.9416  bash                     bash                     /bin/bash
> 16124     2.5872  vmlinux-initrd-7468b0-opf busybox                  /root/vmlinux-initrd-7468b0-opf
> 12276     1.9697  vmlinux-initrd-7468b0-opf bash                     /root/vmlinux-initrd-7468b0-opf
> 7200      1.1553  vmlinux-initrd-7468b0-opf oprofiled                /root/vmlinux-initrd-7468b0-opf
> 7139      1.1455  ld-uClibc-0.9.29.so      busybox                  /lib/ld-uClibc-0.9.29.so
> 4908      0.7875  libuClibc-0.9.29.so      bash                     /lib/libuClibc-0.9.29.so
> 2663      0.4273  vmlinux-initrd-7468b0-opf ophelp                   /root/vmlinux-initrd-7468b0-opf
> 1319      0.2116  ld-uClibc-0.9.29.so      ophelp                   /lib/ld-uClibc-0.9.29.so
> 1282      0.2057  busybox                  busybox                  /bin/busybox
> 1185      0.1901  libuClibc-0.9.29.so      busybox                  /lib/libuClibc-0.9.29.so
> 555       0.0891  ld-uClibc-0.9.29.so      bash                     /lib/ld-uClibc-0.9.29.so
> 462       0.0741  libuClibc-0.9.29.so      oprofiled                /lib/libuClibc-0.9.29.so
> 369       0.0592  libuClibc-0.9.29.so      ophelp                   /lib/libuClibc-0.9.29.so
> 208       0.0334  ophelp                   ophelp                   /bin/ophelp
> 40        0.0064  libgcc_s.so.1            bash                     /lib/libgcc_s.so.1
> 11        0.0018  libgcc_s.so.1            ophelp                   /lib/libgcc_s.so.1
> 5        8.0e-04  libdl-0.9.29.so          bash                     /lib/libdl-0.9.29.so
> 
> WHY there is warning while all files can be located???
> warning: /root/vmlinux-initrd-7468b0-opf could not be found.

When the symbol name defaults to the pathname of the binary, it means the binary has no symbol information in it.  I presume that 'objdump -t /bin/bash' tells you there's no symbol information, too.

Try profiling a little test program -- something that will use up a lot of cpu cycles so you can profile it.  Make sure to compile it with -g.  Do you see symbol info for that?

> 
> Is that the reason why no symbol info was dumped?
> 
> How to fix it?
> 
> Thanks,
> Jian
> 
> 
> 
> 
> 
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