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Message #06556
Re: Innodb_buffer_pool_read_requests is zero
Hi,
The INNODB_METRICS are partly duplicating global status variables. I
would actually like to remove them eventually; see
https://jira.mariadb.org/browse/MDEV-15706. This interface was
designed in MySQL before performance_schema was developed. I do not
know if the author considered using status variables.
The regressions that you found were not intentional; we should avoid
changing interfaces within GA releases such as 10.6. The only
intentional change was to remove some "double bookkeeping" and let
some INNODB_METRICS counters reflect counters that are already being
maintained for other reasons, instead of duplicating them.
Some indirection for the counter Innodb_buffer_pool_read_requests was
removed in MDEV-26827: the duplicate global variable
export_vars.innodb_buffer_pool_read_requests was removed and the
status variable should reflect buf_pool.stat.n_page_gets directly.
When diagnosing https://jira.mariadb.org/browse/MDEV-29967 I did see
that counter being incremented. The statement that I used was:
show global status like 'innodb_buffer_pool_read%';
Can you please file a bug with exact steps on how to reproduce this?
Marko
On Fri, May 12, 2023 at 10:12 AM <mariadb@xxxxxxxxxxxxxx> wrote:
>
> Figured out trx_rseg_history_len; it's just disabled by default now. But
> still stumped on Innodb_buffer_pool_read_requests.
>
> On 5/12/2023 2:40 AM, mariadb@xxxxxxxxxxxxxx wrote:
> > I've also noticed that my transaction history length is always zero;
> > that's true on all my 10.6.13 instances (not just Bullseye). Is that
> > information no longer stored here?
> >
> > SELECT `count` FROM information_schema.INNODB_METRICS WHERE name =
> > 'trx_rseg_history_len';
> >
> > On 5/11/2023 11:55 PM, mariadb@xxxxxxxxxxxxxx wrote:
> >> Just upgraded from 10.6.12 to 10.6.13 on a Debian Bullseye system, and
> >> seeing this oddity. Innodb_buffer_pool_read_requests is zero, and
> >> seems to remain at zero no matter what I do (I even tried selecting
> >> all the data from a small table several times in a row with no
> >> change). It's been running a couple hours now; I've restarted it a
> >> couple times. I have 10.6.13 on a few other platforms as well
> >> (including Buster), and I'm not seeing the same issue on them. What
> >> would cause this? I have no other Bullseye systems running 10.6.13
> >> yet, and the same system has been running 10.6.12 for over a week now
> >> without showing this issue.
> >>
> >> The system _seems_ to be running fine, it's a replica system that is
> >> being fed actively from the master (data comes in to it very regularly).
> >>
> >> MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'innodb_buffer_pool_%';
> >> +-----------------------------------------+--------------------------------------------------+
> >> | Variable_name | Value |
> >> +-----------------------------------------+--------------------------------------------------+
> >> | Innodb_buffer_pool_dump_status | |
> >> | Innodb_buffer_pool_load_status | Buffer pool(s) load
> >> completed at 230511 23:21:26 |
> >> | Innodb_buffer_pool_resize_status | |
> >> | Innodb_buffer_pool_load_incomplete | OFF |
> >> | Innodb_buffer_pool_pages_data | 609103 |
> >> | Innodb_buffer_pool_bytes_data | 9979543552
> >> |
> >> | Innodb_buffer_pool_pages_dirty | 19465 |
> >> | Innodb_buffer_pool_bytes_dirty | 318914560
> >> |
> >> | Innodb_buffer_pool_pages_flushed | 0 |
> >> | Innodb_buffer_pool_pages_free | 299441 |
> >> | Innodb_buffer_pool_pages_made_not_young | 0 |
> >> | Innodb_buffer_pool_pages_made_young | 107 |
> >> | Innodb_buffer_pool_pages_misc | 0 |
> >> | Innodb_buffer_pool_pages_old | 224824 |
> >> | Innodb_buffer_pool_pages_total | 908544 |
> >> | Innodb_buffer_pool_pages_lru_flushed | 0 |
> >> | Innodb_buffer_pool_pages_lru_freed | 0 |
> >> | Innodb_buffer_pool_pages_split | 726 |
> >> | Innodb_buffer_pool_read_ahead_rnd | 0 |
> >> | Innodb_buffer_pool_read_ahead | 3 |
> >> | Innodb_buffer_pool_read_ahead_evicted | 0 |
> >> | Innodb_buffer_pool_read_requests | 0 |
> >> | Innodb_buffer_pool_reads | 604346 |
> >> | Innodb_buffer_pool_wait_free | 0 |
> >> | Innodb_buffer_pool_write_requests | 3639341 |
> >> +-----------------------------------------+--------------------------------------------------+
> >> 25 rows in set (0.000 sec)
> >>
> >> MariaDB [(none)]> SHOW VARIABLES LIKE 'innodb_buffer_pool%';
> >> +-------------------------------------+----------------+
> >> | Variable_name | Value |
> >> +-------------------------------------+----------------+
> >> | innodb_buffer_pool_chunk_size | 134217728 |
> >> | innodb_buffer_pool_dump_at_shutdown | ON |
> >> | innodb_buffer_pool_dump_now | OFF |
> >> | innodb_buffer_pool_dump_pct | 80 |
> >> | innodb_buffer_pool_filename | ib_buffer_pool |
> >> | innodb_buffer_pool_load_abort | OFF |
> >> | innodb_buffer_pool_load_at_startup | ON |
> >> | innodb_buffer_pool_load_now | OFF |
> >> | innodb_buffer_pool_size | 15032385536 |
> >> +-------------------------------------+----------------+
> >> 9 rows in set (0.000 sec)
> >>
> >> _______________________________________________
> >> Mailing list: https://launchpad.net/~maria-discuss
> >> Post to : maria-discuss@xxxxxxxxxxxxxxxxxxx
> >> Unsubscribe : https://launchpad.net/~maria-discuss
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> >
> > _______________________________________________
> > Mailing list: https://launchpad.net/~maria-discuss
> > Post to : maria-discuss@xxxxxxxxxxxxxxxxxxx
> > Unsubscribe : https://launchpad.net/~maria-discuss
> > More help : https://help.launchpad.net/ListHelp
> >
>
> _______________________________________________
> Mailing list: https://launchpad.net/~maria-discuss
> Post to : maria-discuss@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~maria-discuss
> More help : https://help.launchpad.net/ListHelp
--
Marko Mäkelä, Lead Developer InnoDB
MariaDB plc
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