Unhelpful warning: Warning, unable to set nice value

[ole-tange]

When nicing lrz you get the following unhelpful warning:

$ echo | nice nice lrz | wc
Warning, unable to set nice value
Warning, unable to set nice value on thread
Warning, unable to set nice value on thread
      3       2      70

According to top lrz is niced as expected, so the warning is only confusing.

[pete4abw]

Nice is set internally in the program via -N option. There is no test for external use of the nice command. Should there be?

[pete4abw]

Because nice is set with the command line option -N. The default is 19.

There is no internal test for external nice usage.

Why would you do this command anyway?

On Thu, 24 Oct 2019 15:59:08 -0700 Ole Tange notifications@github.com wrote:

Running this:

$ echo | nice nice lrz | wc

should not give a warning. I have no opinion how to solve it.

-- Peter Hyman (609)598-0262 (612)440-7383 (Pete)

[ole-tange]

The situation I discovered this in was a script that was called with nice and which included lrz; so lrz simply inherited the nice value. And I was surprised to see a script that normally worked just fine, now giving warnings.

Most UNIX commands I know will not renice themselves without explicitly being told to. They will let the user decide whether they should be niced or not. I am not sure renicing without telling the user adheres to Principle of Least Surprise.

It seems backwards that the user will have to know lrz quite intimately to have it run at the same nice level as it is called. I have used lrz for several years and even I do not know what options to give lrz to make it run at the same nice level as its parent without giving warnings.

I had hoped lrz could be used as a drop-in replacement for gzip, but this behaviour is different from gzip, and if it is not changed, I hope at least it will be stressed in the man page.

lrz already behaves slightly different from lrzip. Maybe it would make sense to simply remove the renicing when called as lrz?

That solution would fit well with the description from the man page:

lrz is identical to the lrzip application, however, its command line options and behaviour
are made to be as compatible with gzip as possible.

[pete4abw]

BTW the same warning occurs using lrzip or lrzcat. It's not specific to lrz, as expected.

$ echo | nice nice lrzip  | wc
Warning, unable to set nice value
Compression Ratio: inf. Average Compression Speed:  0.000MB/s.
Total time: 00:00:00.00
      3       3       70

However, setting -N ## as a command line option, works fine.

$ echo | lrz -N 19 | wc
      3       3      70

It's an interesting exercise, but since lrzip handles niceness internally, is documented as such, and performs this function as intended, I would say this is not a bug, but a usage error.

[ole-tange]

When I run lrz, it runs at nice level 0. main.c says:

                control->nice_val = 0;

The manual for lrz says: "lrz is identical to the lrzip application, however, its command line options and behaviour are made to be as compatible with gzip as possible."

For that reason I think it would be fair that the setpriority is simply skipped if -N is not set when called as lrz. So:

diff --git a/main.c b/main.c                                                                                                                                                
index f3391a8..de8ba22 100644                                                                                                                                               
--- a/main.c                                                                                                                                                                
+++ b/main.c                                                                                                                                                                
@@ -304,10 +304,11 @@ static void recurse_dirlist(char *indir, char **dirlist, int *entries)                                                                                

 static const char *loptions = "bcCdDefghHiKlL:nN:o:O:p:PqrS:tTUm:vVw:z?";                                                                                                  
 static const char *coptions = "bcCdefghHikKlLnN:o:O:p:PrS:tTUm:vVw:z?123456789";                                                                                           
+static bool compat = false;                                                                                                                                                

 int main(int argc, char *argv[])                                                                                                                                           
 {                                                                                                                                                                          
-   bool lrzcat = false, compat = false, recurse = false;
+ bool lrzcat = false, recurse = false;
        bool options_file = false; /* for environment and tracking of compression setting */
        struct timeval start_time, end_time;
        struct sigaction handler;
@@ -569,8 +570,12 @@ int main(int argc, char *argv[])
                if (unlikely(setpriority(PRIO_PROCESS, 0, control->nice_val / 2) == -1))
                        print_err("Warning, unable to set nice value\n");
        } else {
-           if (unlikely(setpriority(PRIO_PROCESS, 0, control->nice_val) == -1))
+   if(compat && !control->nice_val) {
+     /* Skip */
+   } else {
+     if (unlikely(setpriority(PRIO_PROCESS, 0, control->nice_val) == -1))
                        print_err("Warning, unable to set nice value\n");
+   }
        }

        /* One extra iteration for the case of no parameters means we will default to stdin/out */
diff --git a/stream.c b/stream.c
index 4dd2d82..42e7c42 100644
--- a/stream.c
+++ b/stream.c
@@ -91,6 +91,7 @@ static long output_thread;
 static pthread_mutex_t output_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t output_cond = PTHREAD_COND_INITIALIZER;
 static pthread_t *threads;
+static bool compat;

 bool init_mutex(rzip_control *control, pthread_mutex_t *mutex)
 {
@@ -1276,9 +1277,10 @@ static void *compthread(void *data)
        cti = &cthread[i];
        ctis = cti->sinfo;

+ if(compat) {
        if (unlikely(setpriority(PRIO_PROCESS, 0, control->nice_val) == -1))
                print_err("Warning, unable to set nice value on thread\n");
-
+ }
        cti->c_type = CTYPE_NONE;
        cti->c_len = cti->s_len;

[pete4abw]

This issue was dealt with in #136 . Issue can be closed.

[ckolivas]

Unfortunately #136 did not address this problem, but I will shortly.