scylla_prepare + scylla_cpuset_setup: make scylla_cpuset_setup idempo…

…tent without introducing regressions

This patch fixes the regression introduced by 3a51e78 which broke
a very important contract: perftune.yaml should not be "touched"
by Scylla scriptology unless explicitly requested.

And a call for scylla_cpuset_setup is such an explicit request.

The issue that the offending patch was intending to fix was that
cpuset.conf was always generated anew for every call of
scylla_cpuset_setup - even if a resulting cpuset.conf would come
out exactly the same as the one present on the disk before tha call.

And since the original code was following the contract mentioned above
it was also deleting perftune.yaml every time too.
However, this was just an unavoidable side-effect of that cpuset.conf
re-generation.

The above also means that if scylla_cpuset_setup doesn't write to cpuset.conf
we should not "touch" perftune.yaml and vise versa.

This patch implements exactly that together with reverting the dangerous
logic introduced by 3a51e78.

Fixes scylladb#11385
Fixes scylladb#10121

dist/common/scripts/scylla_cpuset_setup

@@ -36,6 +36,9 @@ if __name__ == '__main__':
     except:
         pass
     if cpuset != args.cpuset or smp != args.smp:
+        if os.path.exists('/etc/scylla.d/perftune.yaml'):
+            os.remove('/etc/scylla.d/perftune.yaml')
+
         cfg.set('CPUSET', '{cpuset}{smp}'.format( \
                 cpuset='--cpuset {} '.format(args.cpuset) if args.cpuset else '', \
                 smp='--smp {} '.format(args.smp) if args.smp else '' \

dist/common/scripts/scylla_prepare

@@ -62,16 +62,6 @@ def get_irq_cpu_mask():
 
     return out(hwloc_cmd).strip()
 
-def config_updated():
-    perftune_mtime = os.path.getmtime('/etc/scylla.d/perftune.yaml')
-    cpuset_mtime = os.path.getmtime('/etc/scylla.d/cpuset.conf')
-    sysconfig_mtime = os.path.getmtime(sysconfdir_p() / 'scylla-server')
-    print("perftune_mtime < cpuset_mtime:{}".format(perftune_mtime < cpuset_mtime))
-    print("perftune_mtime < sysconfig_mtime:{}".format(perftune_mtime < sysconfig_mtime))
-    if perftune_mtime < cpuset_mtime or perftune_mtime < sysconfig_mtime:
-        return True
-    return False
-
 def create_perftune_conf(cfg):
     """
     This function checks if a perftune configuration file should be created and
@@ -97,7 +87,7 @@ def create_perftune_conf(cfg):
         params += ' --write-back-cache=false'
 
     if len(params) > 0:
-        if os.path.exists('/etc/scylla.d/perftune.yaml') and not config_updated():
+        if os.path.exists('/etc/scylla.d/perftune.yaml'):
             return True
 
         params += ' --dump-options-file'