MDEV created for this topic: https://mariadb.atlassian.net/browse/MDEV-5019
i will need some help with internals, could anyone give me some points where i could get variables about thread pool groups? 2013/9/16 Roberto Spadim <robe...@spadim.com.br> > Hi Michael! > > 2013/9/16 Michael Paulini <michael.paul...@wormbase.org> > >> Hi Roberto, >> >> I do believe the idea of the thread pool was to get rid of the one >> thread/connection paradigm, so all connections will be served by >> potentially all threads. >> > > Yes the idea of thread pool from > https://mariadb.com/kb/en/thread-pool-in-mariadb-51-53/ and > https://mariadb.com/kb/en/threadpool-in-55/ is ok, handle many > connections in less threads, and use better hardware resources (with some > problems with meta data locks, deadlocks, and others locks) > but let me explain my doubts... > *1) *what's the name of this "task selector", internally (and at worklog > 246) i see a scheduler.cc file, should i call this as threads scheduler? > from that file there're three kinds o schedulers "one-process-per-thread" > and "pool-of-threads" and "no-thread" right? > i think that's the right name to this part of code that select what query > will "work" is "scheduler", isn't? i will use it in this email > > *2) *what's the internal or maybe the complete name of ID column of > processlist? > internally i know it's the "->thread_id" of THD class variable, from > sql_show.cc: > > /* ID */ > table->field[0]->store((longlong) tmp->thread_id, TRUE); > > i know that processlist is a very old code, maybe from mysql 3.23 and at > that time we had only threads, and no thread pool > now we have three schedulers and maybe the ->thread_id is a old var name, > that should be called "connection_id" > but changing this name is a big patch without rewards, and a bad reward of > incompatibility with plugins and others external tools that use THD class, > i'm right? > > if yes, maybe we could add more information at > information_schema.processlist, with a comment about the real name, just to > remove the wrong idea about "ID", something like: > > CREATE TABLE `PROCESSLIST` (`ID` BIGINT(4) NOT NULL DEFAULT '0'* COMMENT > "INTERNAL CONNECTION ID or something better?"*,`QUERY_ID` BIGINT(4) NOT NULL > DEFAULT '0',`USER` VARCHAR(128) NOT NULL DEFAULT '',`HOST` VARCHAR(64) NOT > NULL DEFAULT '',`DB` VARCHAR(64) NULL DEFAULT NULL,`COMMAND` VARCHAR(16) NOT > NULL DEFAULT '',`TIME` INT(7) NOT NULL DEFAULT '0',`STATE` VARCHAR(64) NULL > DEFAULT NULL,`INFO` LONGTEXT NULL,`TIME_MS` DECIMAL(22,3) NOT NULL DEFAULT > '0.000',`STAGE` TINYINT(2) NOT NULL DEFAULT '0',`MAX_STAGE` TINYINT(2) NOT > NULL DEFAULT '0',`PROGRESS` DECIMAL(7,3) NOT NULL DEFAULT > '0.000',`MEMORY_USED` INT(7) NOT NULL DEFAULT '0',`EXAMINED_ROWS` INT(7) NOT > NULL DEFAULT '0')COLLATE='utf8_general_ci'ENGINE=Aria; > > > *3)* now that ID is better explained in processlist, could we show more > information? > i don't know if it's the right place (processlist table), maybe another > table (thread_pool table) is better, check what i'm talking about... > > i need information about thread pool group, from "Threadpool > implementation on Unix." worklog (maybe the windows implementatition too, > but let's check unix for now), and see what each thread pool is doing > > from worklog, we have this information (i will mark what i think > important): > > Each *group** *in itself is a complete small pool with a *listener thread* > (the one waiting for network events) , work queue (is it a thread or a shared > memory?) and worker threads (see the "s"? threads, more than one worker > thread). > > A group has the responsibility of keeping one thread running, if there is a > work to be done. More than one thread in a group can be running, depending on > circumstances (more about this later). > Clients are *assigned to the groups in a round-robin fashion** (here my > doubt, what client is running in what thread pool group?)*. This will keep > (statistically) about the same ratio of clients per group. > Listener and worker roles are dynamically assigned. Listener can become > worker, after waiting for network events; it can pick an event and handle > thus it becoming a worker. Vice versa, once worker is finished processing a > query, it can become listener. > > wow *-*! it's a very very interesting code, schedulers are something that > i really like =) > now... what the pool is doing? i'm thinking something similar to a > information schema table to help here, check: > > CREATE TABLE information_schema.THREAD_POOL( > thread_pool_group BIGINT NOT NULL DEFAULT 0, > thread_id BIGINT NOT NULL DEFAULT 0, (that's not the THD->thread_id > variable, it's the real system thread, maybe a listerner, a worker or a > work queue (is work queue a thread?) ) > work ENUM('listener','worker','queue') NOT NULL DEFAULT 'queue', (this > show what this thread do in this thread pool group) > connection_id BIGINT DEFAULT 0, (that's the THD->thread_id variable) > > others columns? maybe timeouts and others informations from internall > scheduller? maybe timers for windows or others vars... must check the > scheduller code > ) > > > reading mikael post: > > http://mikaelronstrom.blogspot.com.br/2011/10/mysql-thread-pool-information-schema.html > i think i'm not wrong creating new tables... > > > thanks guys > > > -- > Roberto Spadim > SPAEmpresarial > -- Roberto Spadim SPAEmpresarial
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