Zheyuan Li's questions

I am unable to generate flat profiling result using sprof in Ubuntu 16.04.02 (as well as 14.04.01). Here is a reproducible example, adapted from man sprof.

First create a directory for experiment, then create prog.c and libdemo.c files inside:

// prog.c
       #include <stdlib.h>

       void x1(void);
       void x2(void);

       int
       main(int argc, char *argv[])
       {
           x1();
           x2();
           exit(EXIT_SUCCESS);
       }

// libdemo.c
       #include <unistd.h>

       void
       consumeCpu1(int lim)
       {
           int j;

           for (j = 0; j < lim; j++)
            getppid();
       }

       void
       x1(void) {
           int j;

           for (j = 0; j < 100; j++)
            consumeCpu1(200000);
       }

       void
       consumeCpu2(int lim)
       {
           int j;

           for (j = 0; j < lim; j++)
            getppid();
       }

       void
       x2(void)
       {
           int j;

           for (j = 0; j < 1000; j++)
            consumeCpu2(10000);
       }

Now open a terminal, and change directory to the above created one, then run the following shell script:

cc -g -fPIC -shared -o libdemo.so libdemo.c
cc -g -o prog prog.c -L. -ldemo

export LD_PROFILE=libdemo.so
export LD_PROFILE_OUTPUT=$(pwd)    ## use current directory
rm -f libdemo.so.profile
LD_LIBRARY_PATH=. ./prog
sprof -p libdemo.so libdemo.so.profile

I get an error:

Inconsistency detected by ld.so: dl-open.c: 717: _dl_open: Assertion `_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT' failed!

libdemo.so.profile has been generated without problem, but sprof fails to process it.

I found this Stack Overflow thread What is causing sprof to complain about “inconsistency detected by ld.so”?, but it does not offer a solution. I want to get sprof to work!

Is this problem dependent on Linux distributions? I saw a thread on 2016, where sprof is successful: sprof flat profile name column has ugly format.

Frankly speaking I don't know which is the best forum to post this question. It looks like a programming question that belongs to Stack Overflow, but the C program and profiling runs alright; it is just sprof that fails to process it in the final stage, which should be a Linux related issue. Then if this issue is independent on Linux distributions, I should ask about on Unix & Linux, but if it only occurs on Ubuntu, I should raise it here on ask ubuntu. Well, feel free to migrate it to the best place as you see fit; I have no clue on it at all.

I want to disable Intel "turbo boost" on startup of my system. For reason of this, as well as my laptop details, please refer to my Stack Overflow thread: Why can't my CPU retain peak performance in HPC?

In an answer I made myself, I used the following line inside /etc/rc.local:

echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo

This solution is partly motivated by this thread: Disabling Intel Turbo Boost in ubuntu, and was working just as expected, before I upgrade my Ubuntu system from 14.04 to 16.04 in February. But after that it no longer works: the no_turbo value is still 0 and that line has no effect at all.

Of course, I could manually do the following later:

sudo su
echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
exit

However, I can't remember doing this every time, and it is very discouraging when I realized that I had forgotten to do so and have to rerun a long benchmarking (like what I am doing now).

Is there an explanation why the same solution fails in 16.04? Or how can I achieve this automatically on startup?

Note I have other lines in rc.local, like for turning off Intel hyperthreading and setting backlight, they all work. It is just this particular line for "turbo boost" that fails. So the problem is not that rc.local is not run.

My machine has UEFI boot loader. Though there is an entry for the so-called legacy BIOS, there are few options there to set. Neither hyperthreading nor "turbo boost" can be configured.

In case someone wonders: the

systemctl enable rc-local.service

does not solve the issue.

I am asking this question from an awkward situation. As you may know or not know, Google is blocked in China. A discouraging consequence (at least to me) is that visiting Stack Exchange sites, like Stack Overflow where I used to be very active while I was doing my degree in UK, is very hard. It can take more than 20s to load a page. The problem is that Stack Exchange sites rely on an external JAVA script from

http://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js

but since Google is blocked, this script can't be accessed. But Firefox would spend considerable time trying to get this script. (Note that the jquery version may change in future, but it is 1.12.4 when this question is asked. Use F12 to check the most up-to-date version.)

In fact, this script can be accessed freely from

https://code.jquery.com/jquery-1.12.4.min.js

So, an ideal solution is to redirect the page under Google domain to Jquery domain.

Is this possible by modifying /etc/hosts files? At the moment I am simply doing a brutal webpage blocking:

127.0.0.1    ajax.googleapis.com

Although Firefox now will stop trying to load this script so visiting stack exchange sites becomes as fast as normal, many site features are not useable, like voting etc. So the best solution is a redirection.

If immediate redirection is impossible, then I guess I need to download the JAVA script from Jquery to my laptop, then redirect the googleapis page to my localhost. However, I don't know how to set up a localhost, especially where to place my downloaded script.

Can anyone help me out? Very appreciated.