Re: Thread 140699996440320 has waited at trx0rseg.ic line 50 for 946 seconds
Interestingly, it's pretty much the opposite, a rather lightly used server. It hosts some wordpress site, and according to the Apache logs, there were a series of login attempts from script kiddies at the time, but apparently but not much more.
The mysql logs have more info
BACKGROUND THREAD
-----------------
srv_master_thread loops: 110133 srv_active, 0 srv_shutdown, 5501480 srv_idle
srv_master_thread log flush and writes: 0
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 158488
--Thread 140699996440320 has waited at trx0rseg.ic line 50 for 946 seconds the semaphore:
X-lock on RW-latch at 0x7ff74ff50408 created in file buf0buf.cc line 778
a writer (thread id 140700155893504) has reserved it in mode SX
number of readers 0, waiters flag 1, lock_word: 10000000
Last time read locked in file lob0impl.cc line 1220
Last time write locked in file /var/tmp/portage/dev-db/mysql-community-8.0.21/work/mysql/storage/innobase/buf/buf0flu.cc line 1334
OS WAIT ARRAY INFO: signal count 152272
RW-shared spins 1313, rounds 1786, OS waits 920
RW-excl spins 36740, rounds 1105468, OS waits 37025
RW-sx spins 794, rounds 23820, OS waits 729
Spin rounds per wait: 1.36 RW-shared, 30.09 RW-excl, 30.00 RW-sx
------------
TRANSACTIONS
------------
Trx id counter 4218853
Purge done for trx's n:o < 4218847 undo n:o < 0 state: running
History list length 4
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 422175512738552, not started flushing log
mysql tables in use 1, locked 1
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512737696, not started flushing log
mysql tables in use 1, locked 1
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512736840, not started flushing log
mysql tables in use 1, locked 1
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512735984, not started flushing log
mysql tables in use 1, locked 1
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512735128, not started flushing log
mysql tables in use 1, locked 1
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512734272, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422175512733416, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 1; buffer pool: 0
327850 OS file reads, 3062556 OS file writes, 1908116 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 11 merges
merged operations:
insert 1, delete mark 10, delete 0
discarded operations:
insert 0, delete mark 0, delete 0
Hash table size 34679, node heap has 12 buffer(s)
Hash table size 34679, node heap has 20 buffer(s)
Hash table size 34679, node heap has 4 buffer(s)
Hash table size 34679, node heap has 5 buffer(s)
Hash table size 34679, node heap has 5 buffer(s)
Hash table size 34679, node heap has 13 buffer(s)
Hash table size 34679, node heap has 3 buffer(s)
Hash table size 34679, node heap has 8 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 9876976146
Log buffer assigned up to 9876976146
Log buffer completed up to 9876976146
Log written up to 9876976146
Log flushed up to 9876974648
Added dirty pages up to 9876976146
Pages flushed up to 9876974379
Last checkpoint at 9876974379
978361 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 137363456
Dictionary memory allocated 4374008
Buffer pool size 8192
Free buffers 1024
Database pages 7098
Old database pages 2600
Modified db pages 26
Pending reads 0
Pending writes: LRU 0, flush list 6, single page 0
Pages made young 299871, not young 1427495
0.00 youngs/s, 0.00 non-youngs/s
Pages read 326913, created 12598, written 1542685
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 7098, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Process ID=12465, Main thread ID=140700030011136 , state=sleeping
Number of rows inserted 67801, updated 98095, deleted 65499, read 166470761
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
Number of system rows inserted 6718, updated 26169, deleted 5620, read 35201208
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
But that page you reference doesn't really say a whole lot about how to read this.