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MDEV-15016: multiple page cleaner threads use a lot of CPU

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While the bug was reported as a regression of
MDEV-11025 Make number of page cleaner threads variable dynamic
in MariaDB Server 10.3, the code that MariaDB Server 10.2
inherited from MySQL 5.7.4 (WL#6642) looks prone to similar errors.

pc_flush_slot(): If there is no work to do, reset the is_requested
signal, to avoid potential busy-waiting in
buf_flush_page_cleaner_worker(). If the coordinator thread has shut
down, avoid resetting the is_requested event, to avoid a potential
hang at shutdown if there are multiple worker threads.
This commit is contained in:
Marko Mäkelä 2018-01-24 10:23:52 +02:00
parent 12f900228f
commit ac3e7f788e
1 changed files with 10 additions and 8 deletions
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18
storage/innobase/buf/buf0flu.cc
View File

@ -1,7 +1,7 @@
/*****************************************************************************
Copyright (c) 1995, 2017, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2013, 2017, MariaDB Corporation.
Copyright (c) 2013, 2018, MariaDB Corporation.
Copyright (c) 2013, 2014, Fusion-io
This program is free software; you can redistribute it and/or modify it under
@ -2843,7 +2843,9 @@ pc_flush_slot(void)
mutex_enter(&page_cleaner->mutex);
if (page_cleaner->n_slots_requested > 0) {
if (!page_cleaner->n_slots_requested) {
os_event_reset(page_cleaner->is_requested);
} else {
page_cleaner_slot_t* slot = NULL;
ulint i;
@ -2865,16 +2867,16 @@ pc_flush_slot(void)
page_cleaner->n_slots_flushing++;
slot->state = PAGE_CLEANER_STATE_FLUSHING;
if (page_cleaner->n_slots_requested == 0) {
os_event_reset(page_cleaner->is_requested);
}
if (!page_cleaner->is_running) {
if (UNIV_UNLIKELY(!page_cleaner->is_running)) {
slot->n_flushed_lru = 0;
slot->n_flushed_list = 0;
goto finish_mutex;
}
if (page_cleaner->n_slots_requested == 0) {
os_event_reset(page_cleaner->is_requested);
}
mutex_exit(&page_cleaner->mutex);
lru_tm = ut_time_ms();
@ -2885,7 +2887,7 @@ pc_flush_slot(void)
lru_tm = ut_time_ms() - lru_tm;
lru_pass++;
if (!page_cleaner->is_running) {
if (UNIV_UNLIKELY(!page_cleaner->is_running)) {
slot->n_flushed_list = 0;
goto finish;
}