maria-developers team mailing list archive

[MARK CALLAGHAN <mdcallag@xxxxxxxxx>]

Mutex contention from various plugins


On Tue, Aug 20, 2013 at 9:12 AM, Pavel Ivanov <pivanof@xxxxxxxxxx> wrote:

> Workaround for which problem?
>
> On Tue, Aug 20, 2013 at 8:17 AM, MARK CALLAGHAN <mdcallag@xxxxxxxxx>
> wrote:
> > Is the workaround to use static rather than dynamic plugins?
> >
> >
> > On Tue, Aug 20, 2013 at 7:31 AM, Sergei Golubchik <serg@xxxxxxxxxxx>
> wrote:
> >>
> >> Hi, Pavel!
> >>
> >> On Aug 20, Pavel Ivanov wrote:
> >> > On Tue, Aug 20, 2013 at 1:09 AM, Sergei Golubchik <serg@xxxxxxxxxxx>
> >> > wrote:
> >> > > On Aug 19, Pavel Ivanov wrote:
> >> > >> No, it's not reasonable for semi-sync to lock/unlock LOCK_plugin.
> >> > >> It's plugin infrastructure that does that.
> >> > >>
> >> > >> I've actually was terrified to learn that each call into semi-sync
> >> > >> plugin is surrounded with pthread_rwlock_rdlock/
> >> > >> pthread_rwlock_unlock (which is not cheap I believe). And also for
> >> > >> each such call it "locks"/"unlocks" the semi-sync plugin. And
> >> > >> although "locking" plugin avoids locking LOCK_plugin when plugin is
> >> > >> linked statically, "unlocking" doesn't do that.
> >> > >
> >> > Sure, but macro FOREACH_OBSERVER inside rpl_handler.cc doesn't use
> >> > this function. It uses plugin_unlock_list() which always locks
> >> > LOCK_plugin.
> >> >
> >> > BTW, MariaDB still supports compiling semi-sync plugins dynamically,
> >> > but it seems that it doesn't do anything against unloading semi-sync
> >> > plugins in the middle of transactions. Did anyone think about this?
> >>
> >> Judging from the replication plugin API - I don't think so.
> >>
> >> But if it adds that much overhead, I suppose we'll need to fix it.
> >> Then we fix the unloading too.
> >>
> >> Regards,
> >> Sergei
> >>
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> >
> >
> >
> >
> > --
> > Mark Callaghan
> > mdcallag@xxxxxxxxx
>



-- 
Mark Callaghan
mdcallag@xxxxxxxxx