Mutex contention from various plugins On Tue, Aug 20, 2013 at 9:12 AM, Pavel Ivanov <pivanof@google.com> wrote:
Workaround for which problem?
On Tue, Aug 20, 2013 at 8:17 AM, MARK CALLAGHAN <mdcallag@gmail.com> wrote:
Is the workaround to use static rather than dynamic plugins?
On Tue, Aug 20, 2013 at 7:31 AM, Sergei Golubchik <serg@mariadb.org> wrote:
Hi, Pavel!
On Aug 20, Pavel Ivanov wrote:
On Tue, Aug 20, 2013 at 1:09 AM, Sergei Golubchik <serg@mariadb.org> 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
_______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : maria-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
-- Mark Callaghan mdcallag@gmail.com
-- Mark Callaghan mdcallag@gmail.com