maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Sergey!

On Aug 03, Sergey Vojtovich wrote:
> > On Jun 29, Sergey Vojtovich wrote:
> > > revision-id: 48d1ba6097939efe5efd28dd3ed9d281cc2bc2f4 (mariadb-10.2.0-93-g48d1ba6)
> > > parent(s): 8bec9746f0d5b363f385713035ca3f2daff34e1c
> > > committer: Sergey Vojtovich
> > > timestamp: 2016-06-29 16:33:08 +0400
> > > message:
> > > 
> > > MDEV-10296 - Multi-instance table cache
> > > 
> > > Improve scalability by implementing multi-instance table cache.
> > > 
> > > diff --git a/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result b/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
> > > index e075c64..22b12a9 100644
> > > --- a/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
> > > +++ b/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
> > > @@ -4559,6 +4559,20 @@ NUMERIC_BLOCK_SIZE	1
> > >  ENUM_VALUE_LIST	NULL
> > >  READ_ONLY	NO
> > >  COMMAND_LINE_ARGUMENT	REQUIRED
> > > +VARIABLE_NAME	TABLE_OPEN_CACHE_INSTANCES
> > > +SESSION_VALUE	NULL
> > > +GLOBAL_VALUE	1
> > > +GLOBAL_VALUE_ORIGIN	COMPILE-TIME
> > 
> > Default value 1 and it's not auto-tuned on startup?
> > You think multi-instance table cache is better stay unused? :)
> > If not, either use a reasonable default or, may be, choose it on
> > startup based on my_gencpus()
> Yes, I think multi-instance table cache is better stay unused probably
> in 99% of installations. E.g. 2 CPU / 20 cores / 40 threads Broadwell
> is 95% satisfied by single instance.

Well... If you add a feature that is "better stay unused probably in 99%
of installations" and disable it by default, it will not be used at all.

Let's think how we can make this feature used, is autosizing the only
option?

> > Besides, instead of pointer arithmetics, you could've simply put
> > 
> >    Share_free_tables free_tables[1];
> > 
> > at the end of TDC_element.
> I'll try it. I tend to remember it wasn't very welcome by C99 (I may be very
> wrong though).

I belive we use that in other places, so it must work ok.

Regards,
Sergei
Chief Architect MariaDB
and security@xxxxxxxxxxx