maria-developers team mailing list archive

[Sergey Vojtovich <svoj@xxxxxxxxxxx>]

Hi Sergei,

On Thu, Jun 18, 2015 at 11:04:15AM +0200, Sergei Golubchik wrote:
> Hi, Sergey!
> 
> On Jun 17, svoj@xxxxxxxxxxx wrote:
> > revision-id: 3f0b02351a53e0fcaee8554c2c852fb3da8fe7da
> > parent(s): 5d03dd20a4abbfd9777b619dfd51a6927323955a
> > committer: Sergey Vojtovich
> > branch nick: mariadb
> > timestamp: 2015-06-17 18:55:38 +0400
> > message:
> > 
> > MDEV-7952 - clock_gettime() takes 0.24% in OLTP RO
...skip...

> > @@ -2793,9 +2793,12 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
> >          table->field[4]->store(command_name[tmp->get_command()].str,
> >                                 command_name[tmp->get_command()].length, cs);
> >        /* MYSQL_TIME */
> > -      ulonglong start_utime= tmp->start_time * HRTIME_RESOLUTION + tmp->start_time_sec_part;
> > -      ulonglong utime= start_utime && start_utime < unow.val
> > -                       ? unow.val - start_utime : 0;
> > +      ulonglong utime= tmp->start_utime;
> > +      ulonglong utime_after_query_snapshot= tmp->utime_after_query;
> > +      if (utime < utime_after_query_snapshot)
> > +        utime= utime_after_query_snapshot; // COM_SLEEP
> > +      utime= utime && utime < unow ? unow - utime : 0;
> 
> 1.
> Please add an assert here that utime<=unow. It uses
> microsecond_interval_timer(), which is supposed to be strictly
> increasing (unlike my_hrtime()).
Somehow I thought that interval_timer() is based on per-CPU clock. But
apparently I was wrong.

Nevertheless nothing prevents thread from updating start_utime/utime_after_query
after we saved unow. So this assertion is not very valid.

> 
> 2.
> You might need to update mysqld_list_processes() too.
Right.

Thanks,
Sergey