[Samba] Slow reply to "smbclient -NL localhost" : strace

[Michael Tokarev]

05.11.2024 12:36, Gilles via samba wrote:
> On 04/11/2024 15:11, Rowland Penny via samba wrote:
>> As I said previously, I do not think this has anything to do with
>> Samba. In an earlier post, you had this output when you ran the same
>> command using 'time':
>>
>> real    0m12.500s
>> user    0m0.732s
>> sys     0m0.102s
>>
>> The 'real' time is the total time it took to run the command, but
>> 'user' + 'sys' is the actual time it took for the Samba part of it, in
>> this case 0.834 seconds, the remaining 11.666 seconds is where your
>> problem lies, what is causing this ?
>> That is what you need to trace, what is getting in the way, it doesn't
>> seem to be anything to do with Samba.
>>
>> When it comes down to it, your 'strace' appears to be useless in this
>> context, there is no 'time' involved.
> 
> Thanks. So I'll look elsewhere to understand why that command is taking so long.

Rowland gives unverified information here, and is
adding to the confusion and distracting attention
from actual problem to somewhere else.

time command shows *CPU* time spent in user space
or system space.  There, CPU time spent by the user
space is 0.7s, and in system is 0.1s.

But the rest of the time might be spent in any system
call which is waiting for something.

For example:

  $ time sleep 5
  real	0m5,001s
  user	0m0,001s
  sys	0m0,000s


If smbclient were just to run usleep() function, it will
show exactly the same behavior.

What's happening here, most likely, is that smbclient is
making some network calls and is waiting for the reply.

It might be a DNS problem or samba (configuration) problem,
depending on where and what it is waiting for.

And yes, this will be visible in the strace output.

> FWIW, there's no delay after I run it once… but only for a couple of minutes.

This suggests it might be a name resolution issue.

/mjt