How do you tune innodb_read_io_threads?

The default value of innodb_read_io_threads and innodb_write_io_threads is 4. How do you check if your server load needs a higher number of threads?

As I regularly check show engine innodb status \G, there is no traceable activity:

-------- 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 32 state: waiting for completed aio requests (write thread) I/O thread 33 state: waiting for completed aio requests (write thread) Pending normal aio reads: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] , aio writes: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] , 

Furthermore, what is the downside of increasing it to the maximum value of 64? If not using, they are harmless idle threads.

Which configuration to tune to best-utilize fast SSD

I am doing some testing on the MySQL performance on top of different devices, including SMR-HDD, SAS-HDD, SATA-SSD, NVMe-SSD, Optane-SSD. I want to find configurations that exclusively friendly to specific type(s) of device(s) with respect to performance.

I am using TPC-H benchmark as workload. Could you please suggest some candidate configurations to test?


InnoDB: page_cleaner: settings might not be optimal (how to tune)

I am having similar issues to this question but I’m trying to understand how to tune the database correctly (rather than just lowering settings and hoping 😉

In the error log I have these entries (often days or weeks apart)

2020-12-19T11:54:53.640527Z 0 [Note] InnoDB: page_cleaner: 1000ms intended loop took 12204ms. The settings might not be optimal. (flushed=27 and evicted=0, during the time.) 2020-12-19T23:14:04.901370Z 0 [Note] InnoDB: page_cleaner: 1000ms intended loop took 6788ms. The settings might not be optimal. (flushed=10 and evicted=0, during the time.) 

And corresponding entries in the mysql-slow log! down to the second. What I find weird is that I thought the cleaner was supposed to be some kind of background process… why does it have any impact on the queries themselves?

mysqltuner is happy, the db has 32 gigs ram and some relevant settings are


  1. innodb_page_cleaners is currently 4,
  2. innodb_buffer_pool_instances is 25 !.
  3. innodb_buffer_pool_chunk_size is 134217728
  4. innodb_buffer_pool_size is 26843545600


  1. Should I just set the page cleaners to 25 as suggested in the other answer.
  2. Should I try 1) first, see if it makes a difference, then lower the innodb_lru_scan_depth if I don’t see an improvement?
  3. Why doesn’t MYSQL just default the page cleaners to be the same as the number of instances if it can have such a drastic affect? t suggests setting the page cleaners to the same as the pool instances. Why doesn’t MYSQL just default to that if it’s so sensible?
  4. Is it expected to see the cleaner have an impact in the slow-query log?


How to tune /etc/fstab for HDD read performance in ubuntu servers?

If I want to get the most of my HDDs what are the best fstab settings?

This is a server, with very low risk of losing power, and I have a full backup of everything, so increasing performance at any cost is acceptable.

The disks will be mostly used for reading, almost no writing.

I couldn’t find anything useful on google, so thanks in advance!

Tune a LEMP stack

I don’t have much experience or know much about servers and networks. I am playing around with a VPS that has 2GB Ram and a single core. I h… | Read the rest of

AF tune first time help

I’ve purchased a second hand Nikon D810 and have recently started discovering a few focus problems. Since i shoot alot of theatre and things get printed big quite alot, having things with precise focus is a big issue for me.

I also find colour issues a problem on this D810, but thats another question, so i’ll leave that for today!

I thought maybe i would look into doing a fine tune of my lenses but since i’ve never done this I thought I’d ask a few questions.

Firstly, if there are any good tutorials on Nikon AF tuning you would recommend please do so. I have no idea!

1/ I am assuming I have to AF tune every lens differently but does that mean when I put that lens on the camera will recognise the new AF tuning or it that something i have to set every time?

2/ Should I clean my contacts? Would that also help?

3/ One of my lenses is a Sigma 70-200mm 2.8 and 50mm 1.8 and both bought in 2006 so 12 years old – could the fact they are oldish lenses be one of the factors in the focus problems (tho i’ve never had any major problems with my D800 before it)

Thank you for your time!

K .