Re: Dar architecture questions

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[...]
>>>>
>>>>> My systems are stock ubuntu server 10.04 LTS and debian 6 all on 64bit
>>>>> versions of the OS.
> 
> Are they multi-core or multiprocessors host? Mine in an not very recent
> 64bits mono processor host. Linux kernel used had SMP disabled at
> compilation time. This might have an impact.
> 
> 
>> They are a mix of dual processor single-core (hyperthreading enabled) 
>> older Intel Xeons and newer AMD Opteron quad-core dual processor.  So if 
>> you have SMP disabled in the kernel that could definitely be a 
>> difference.  Perhaps it's some sort of race condition with the 
>> rt_sigprocmask or the mutex lock/unlock that surrounds it.

Reviewing library and system calls documentation, I've noted an error in
the way libdar handles signals. By default, libdar is thread safe and
should not call sigprocmask but pthread_sigmask instead, well dar itself
is single-threaded so this is not a problem here (it is for kdar
graphical multi-threaded application that relies on libdar). On my
system, I see no significant difference in execution time nor in system
call used (both ways still result in rt_sigprocmask as show by strace).

Could you apply the following patch and see if you get any difference on
one of your multi-core host?

diff --git a/src/libdar/tools.cpp b/src/libdar/tools.cpp
index 2ce62a3..e54e4e0 100644
- --- a/src/libdar/tools.cpp
+++ b/src/libdar/tools.cpp
@@ -1635,13 +1635,21 @@ namespace libdar
        sigset_t all;

        sigfillset(&all);
+#if HAVE_LIBPTHREAD
+       if(pthread_sigmask(SIG_BLOCK, &all, &old_mask) != 0)
+#else
        if(sigprocmask(SIG_BLOCK, &all, &old_mask) != 0)
+#endif
            throw Erange("tools_block_all_signals",
string(dar_gettext("Cannot block signals: "))+strerror(errno));
     }

     void tools_set_back_blocked_signals(sigset_t old_mask)
     {
+#if HAVE_LIBPTHREAD
+       if(pthread_sigmask(SIG_SETMASK, &old_mask, NULL))
+#else
        if(sigprocmask(SIG_SETMASK, &old_mask, NULL))
+#endif
            throw Erange("tools_set_back_block_all_signals",
string(dar_gettext("Cannot unblock signals: "))+strerror(errno));
     }



> 
>> Did you see my comment in the previous post about the patch?  I was 
>> thinking that with -v it would display all 1.7 million files instead of 
>> just the status messages which is why I had checked the quiet flag 
>> instead or adding a new command line flag to just get verbose program 
>> status and not file listing.

Yes, I've seen it. By default, dar only report errors met and a summary
at the end of execution. --quiet option suppresses the summary and dar
then report nothing excepted the let errors. --verbose option adds step
by step information about what's going on, including which file is being
processed (not the one skipped, which is activated by -vs). So by
coherence with that, I cannot add the report that are useful for you in
that situation.

I will add a switch that let dar show the different steps it is inside
of, without showing processed files. However this would not take place
in 2.4.x but in 2.5.x. Sorry for that.

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