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這篇文章主要介紹“checkpoint中用于控制刷盤頻率的函數(shù)是什么”,在日常操作中,相信很多人在checkpoint中用于控制刷盤頻率的函數(shù)是什么問題上存在疑惑,小編查閱了各式資料,整理出簡(jiǎn)單好用的操作方法,希望對(duì)大家解答”checkpoint中用于控制刷盤頻率的函數(shù)是什么”的疑惑有所幫助!接下來,請(qǐng)跟著小編一起來學(xué)習(xí)吧!
宏定義
checkpoints request flag bits
checkpoints request flag bits,檢查點(diǎn)請(qǐng)求標(biāo)記位定義.
/* * OR-able request flag bits for checkpoints. The "cause" bits are used only * for logging purposes. Note: the flags must be defined so that it's * sensible to OR together request flags arising from different requestors. */ /* These directly affect the behavior of CreateCheckPoint and subsidiaries */ #define CHECKPOINT_IS_SHUTDOWN 0x0001 /* Checkpoint is for shutdown */ #define CHECKPOINT_END_OF_RECOVERY 0x0002 /* Like shutdown checkpoint, but * issued at end of WAL recovery */ #define CHECKPOINT_IMMEDIATE 0x0004 /* Do it without delays */ #define CHECKPOINT_FORCE 0x0008 /* Force even if no activity */ #define CHECKPOINT_FLUSH_ALL 0x0010 /* Flush all pages, including those * belonging to unlogged tables */ /* These are important to RequestCheckpoint */ #define CHECKPOINT_WAIT 0x0020 /* Wait for completion */ #define CHECKPOINT_REQUESTED 0x0040 /* Checkpoint request has been made */ /* These indicate the cause of a checkpoint request */ #define CHECKPOINT_CAUSE_XLOG 0x0080 /* XLOG consumption */ #define CHECKPOINT_CAUSE_TIME 0x0100 /* Elapsed time */
WRITES_PER_ABSORB
/* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */ //調(diào)用AbsorbSyncRequests的間隔,默認(rèn)值為1000 #define WRITES_PER_ABSORB 1000
CheckpointWriteDelay
CheckpointWriteDelay,控制checkpoint的頻率,邏輯不復(fù)雜,判斷checkpoint flags非CHECKPOINT_IMMEDIATE/非shutdown_requested/非CHECKPOINT_IMMEDIATE并且checkpoint處于調(diào)度中,如滿足上述條件,則調(diào)用AbsorbSyncRequests處理sync,休眠100ms;不如滿足上述條件,則absorb_counter計(jì)數(shù)器減一,如計(jì)數(shù)器≤0,則調(diào)用AbsorbSyncRequests處理sync.
/* * CheckpointWriteDelay -- control rate of checkpoint * 控制checkpoint的頻率 * * This function is called after each page write performed by BufferSync(). * It is responsible for throttling BufferSync()'s write rate to hit * checkpoint_completion_target. * * The checkpoint request flags should be passed in; currently the only one * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes. * * 'progress' is an estimate of how much of the work has been done, as a * fraction between 0.0 meaning none, and 1.0 meaning all done. */ void CheckpointWriteDelay(int flags, double progress) { static int absorb_counter = WRITES_PER_ABSORB; /* Do nothing if checkpoint is being executed by non-checkpointer process */ if (!AmCheckpointerProcess()) return; /* * Perform the usual duties and take a nap, unless we're behind schedule, * in which case we just try to catch up as quickly as possible. */ if (!(flags & CHECKPOINT_IMMEDIATE) &&//非CHECKPOINT_IMMEDIATE !shutdown_requested &&//非關(guān)閉請(qǐng)求 !ImmediateCheckpointRequested() &&//非CHECKPOINT_IMMEDIATE IsCheckpointOnSchedule(progress))//處于checkpoint調(diào)度中 { if (got_SIGHUP) { got_SIGHUP = false; ProcessConfigFile(PGC_SIGHUP); /* update shmem copies of config variables */ UpdateSharedMemoryConfig(); } //Absorb吸收(處理)同步請(qǐng)求 AbsorbSyncRequests(); //重置為WRITES_PER_ABSORB(1000) absorb_counter = WRITES_PER_ABSORB; //檢查歸檔是否超時(shí) CheckArchiveTimeout(); /* * Report interim activity statistics to the stats collector. */ //統(tǒng)計(jì)信息 pgstat_send_bgwriter(); /* * This sleep used to be connected to bgwriter_delay, typically 200ms. * That resulted in more frequent wakeups if not much work to do. * Checkpointer and bgwriter are no longer related so take the Big * Sleep. */ //休眠100ms pg_usleep(100000L); } else if (--absorb_counter <= 0)//Absorb計(jì)數(shù)器減一 { //如計(jì)數(shù)器小于等于0 /* * Absorb pending fsync requests after each WRITES_PER_ABSORB write * operations even when we don't sleep, to prevent overflow of the * fsync request queue. */ //Absorb同步請(qǐng)求 AbsorbSyncRequests(); //重置計(jì)數(shù)器 absorb_counter = WRITES_PER_ABSORB; } }
到此,關(guān)于“checkpoint中用于控制刷盤頻率的函數(shù)是什么”的學(xué)習(xí)就結(jié)束了,希望能夠解決大家的疑惑。理論與實(shí)踐的搭配能更好的幫助大家學(xué)習(xí),快去試試吧!若想繼續(xù)學(xué)習(xí)更多相關(guān)知識(shí),請(qǐng)繼續(xù)關(guān)注億速云網(wǎng)站,小編會(huì)繼續(xù)努力為大家?guī)砀鄬?shí)用的文章!
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