Pt53-Optimització
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Guillem Solà i Boeck (host A10BPC22)
Fent servir scripts de monitorització per optimitzar el rendiment de l'SGBD
- Indicar quins scripts i eines de monitoratge hi ha de BBDD
- Identificar diferents tipus d'optimització: emmagatzematge, espai de disc i procediments de transferències i comunicacions. Indica els resultats obtinguts.
- Identifica tècniques d'optimització de consultes en un SGBD. Indica els resultats obtinguts.
Fer les modificacions al fitxer de configuració que es necessitin
Indicar quins scripts i eines de monitoratge hi ha de BBDD
- Un script escrit en Perl és molt conegut en el món MariaDB/MySQL. Es tracta de mysqltuner.
- Un altre script conegut com a mysql tuning primer. Aquest està escrit en bash i és molt semblant a l'anterior a nivell de funcionalitat.
- El Percona Toolkit és tota una caixa d'eines per a monitoritzar i extreure informació llegible per persones humanes des d'un SGBD.
Com a conclusió, crec que aquests 2 scripts hem de veure'ls com un conjunt ja que és difícil dir si un és millor que l'altre. Com a administradors de sistemes hem de ser capaços de poder treure bones conclusions a partir dels resultats de cadascun.
Identificar diferents tipus d'optimització
- Emmagatzematge
- A nivell d'emmagatzematge es pot destacar el tipus de suport on tindrem instal·lat el sistema operatiu+SGBD i les dades de la Base de Dades en general. Com a norma general, descartarem discos durs mecànics perquè tenen temps d'accés molt lents en comparació als discos durs sòlids (SSD) basats en memòria flash. Encara que el SGBD carregarà les dades més accedides en RAM per a evitar lectures a disc (infinitament més lentes encara que es llegeixi d'un SSD), sempre serà millor un disc ràpid per si s'ha de fer una consulta sobre unes dades que no estiguin cachejades en memòria.
- Espai de disc
- Generalment, com més espai disponible en disc, millor en termes d'escalabilitat del sistema que suporta el SGBD; de manera que no fem curt al cap d'un temps quan la BBDD creixi i haguem de migrar a discos durs més grans o, fins i tot, haver de canviar el servidor sencer. El que és interessant és trobar un balanç entre rendiment de velocitat i espai disponible; ja que com més gran sigui el disc, més car serà. Això potser no és problema per una empresa més o menys gran, però normalment, a les empreses, els sol costar bastant buidar la butxaca per a equipament informàtic i aquest tema serà més delicat. Per tant, tampoc podem donar una conclusió genèrica sinó que haurem d'estudiar cada cas en concret i prendre decisions basant-nos en aquella situació.
- Procediments de transferències i comunicacions
- Per suposat que l'estàndard de comunicacions serà a velocitat de gigabit per qüestions òbvies. Llavors el servidor hauria de tenir, com a mínim, 2 targetes de xarxa en sistema failover per a evitar downtimes en cas que una interfície falli o tingui problemes.
Exemple de funcionament
MySQL Tuning Primer
Per a utilitzar aquest script necessitem tenir instal·lat el programari bc. L'instal·larem amb
yum install bc -y
Una vegada instal·lat el podem fer executable amb
chmod +x tuning-primer.sh
i executar-lo pròpiament amb
./tuning-primer.sh
El meu resultat d'execució és el següent:
Using login values from ~/.my.cnf
- INITIAL LOGIN ATTEMPT FAILED -
Testing for stored webmin passwords:
None Found
Could not auto detect login info!
Found potential sockets: /var/lib/mysql/mysql.sock
Using: /var/lib/mysql/mysql.sock
Would you like to provide a different socket?: [y/N] n
Do you have your login handy ? [y/N] : n
User: root
Password: asix
Would you like me to create a ~/.my.cnf file for you? [y/N] : y
-- MYSQL PERFORMANCE TUNING PRIMER --
- By: Matthew Montgomery -
MySQL Version 5.5.56-MariaDB x86_64
Uptime = 0 days 1 hrs 10 min 48 sec
Avg. qps = 4
Total Questions = 19165
Threads Connected = 1
Warning: Server has not been running for at least 48hrs.
It may not be safe to use these recommendations
To find out more information on how each of these
runtime variables effects performance visit:
http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html
Visit http://www.mysql.com/products/enterprise/advisors.html
for info about MySQL's Enterprise Monitoring and Advisory Service
SLOW QUERIES
The slow query log is NOT enabled.
Current long_query_time = 10.000000 sec.
You have 0 out of 19186 that take longer than 10.000000 sec. to complete
Your long_query_time seems to be fine
BINARY UPDATE LOG
The binary update log is NOT enabled.
You will not be able to do point in time recovery
See http://dev.mysql.com/doc/refman/5.5/en/point-in-time-recovery.html
WORKER THREADS
Current thread_cache_size = 0
Current threads_cached = 0
Current threads_per_sec = 1
Historic threads_per_sec = 0
Your thread_cache_size is fine
MAX CONNECTIONS
Current max_connections = 151
Current threads_connected = 1
Historic max_used_connections = 8
The number of used connections is 5% of the configured maximum.
You are using less than 10% of your configured max_connections.
Lowering max_connections could help to avoid an over-allocation of memory
See "MEMORY USAGE" section to make sure you are not over-allocating
INNODB STATUS
Current InnoDB index space = 6 M
Current InnoDB data space = 17 M
Current InnoDB buffer pool free = 88 %
Current innodb_buffer_pool_size = 128 M
Depending on how much space your innodb indexes take up it may be safe
to increase this value to up to 2 / 3 of total system memory
MEMORY USAGE
Max Memory Ever Allocated : 294 M
Configured Max Per-thread Buffers : 419 M
Configured Max Global Buffers : 272 M
Configured Max Memory Limit : 691 M
Physical Memory : 487 M
Max memory limit exceeds 90% of physical memory
KEY BUFFER
Current MyISAM index space = 462 K
Current key_buffer_size = 128 M
Key cache miss rate is 1 : 81
Key buffer free ratio = 81 %
Your key_buffer_size seems to be fine
QUERY CACHE
Query cache is supported but not enabled
Perhaps you should set the query_cache_size
SORT OPERATIONS
Current sort_buffer_size = 2 M
Current read_rnd_buffer_size = 256 K
Sort buffer seems to be fine
JOINS
./tuning-primer.sh: line 402: export: `2097152': not a valid identifier
Current join_buffer_size = 132.00 K
You have had 0 queries where a join could not use an index properly
Your joins seem to be using indexes properly
OPEN FILES LIMIT
Current open_files_limit = 1024 files
The open_files_limit should typically be set to at least 2x-3x
that of table_cache if you have heavy MyISAM usage.
Your open_files_limit value seems to be fine
TABLE CACHE
Current table_open_cache = 400 tables
Current table_definition_cache = 400 tables
You have a total of 89 tables
You have 93 open tables.
The table_cache value seems to be fine
TEMP TABLES
Current max_heap_table_size = 16 M
Current tmp_table_size = 16 M
Of 559 temp tables, 6% were created on disk
Created disk tmp tables ratio seems fine
TABLE SCANS
Current read_buffer_size = 128 K
Current table scan ratio = 0 : 1
read_buffer_size seems to be fine
TABLE LOCKING
Current Lock Wait ratio = 0 : 19444
Your table locking seems to be fine
MySQL Tuner
Per al MySQL Tuner necessitem una llibreria de Perl que haurem d'instal·lar, sinó l'script no podrà córrer.
yum install -y perl-Switch
Una vegada instal·lat, executarem l'script especificant que volem veure recomanacions, ja que per defecte només se'ns llistaran els paràmetres i els seus valors actuals, només. També haurem d'especificar un arxiu de configuració d'execució; jo he triat un default que ja ve:
perl mysqltuner.pl --recommend --config tuner-default.cnf
Uptime in seconds: 4479.00
Uptime: 1h 14m 39s
Questions: 22558.00
% slow queries: 0.00
slow query rate: 0.00 per day
Long query time: 10.00
Slow query logging: OFF
% reads: 94.77
% writes: 5.23
qps: 5.04
reads per sec: 18.28 per day
writes per sec: 1.01 per day
Queries: 5.04 per second
Connections: 560.00
Bytes sent: 98 Million
Bytes received: 4 Million
Supported Version: 5
Release Series: 5.5
Minor Version: 56
Distribution: MariaDB Server
Distribution: MariaDB Server
MySQL Architecture: x86_64
Query cache efficiency (%): 0.00
Use of uninitialized value $num in pattern match (m//) at mysqltuner.pl line
223 (#1)
(W uninitialized) An undefined value was used as if it were already
defined. It was interpreted as a "" or a 0, but maybe it was a mistake.
To suppress this warning assign a defined value to your variables.
To help you figure out what was undefined, perl will try to tell you
the name of the variable (if any) that was undefined. In some cases
it cannot do this, so it also tells you what operation you used the
undefined value in. Note, however, that perl optimizes your program
anid the operation displayed in the warning may not necessarily appear
literally in your program. For example, "that $foo" is usually
optimized into "that " . $foo, and the warning will refer to the
concatenation (.) operator, even though there is no . in
your program.
Use of uninitialized value $compval in concatenation (.) or string at
mysqltuner.pl line 230 (#1)
Use of uninitialized value in string eq at mysqltuner.pl line 231 (#1)
% query cache used:
Query cache low memory prunes: 0.00 per day
Query cache size: 0 bytes
Query cache min result size: 1.0 Mb
Total sorts: 1.00
% sorts that cause temporary tables: 0.00
rate of sorts that cause temporary tables: 0.00 per day
sort_buffer_size: 2.0 Mb
read_rnd_buffer_size: 256.0 Kb
Sort rows: 16.88 per hour
rate of joins without indexes: 6.70 per minute
rate of reading first index entry: 1.46 per minute
rate of reading fixed position: 28.13 per hour
rate of reading next table row: 53.50 per minute
tmp_table_size-max_heap_table_size: 0.00
tmp_table_size: 16.0 Mb
max_heap_table_size: 16.0 Mb
% temp disk tables: 5.61
temp disk rate: 28.94 per hour
temp table rate: 8.12 per minute
MyISAM key buffer size: 128.0 Mb
max % MyISAM key buffer ever used: 0.22
% MyISAM key buffer used: 18.45
% index reads from memory: 99.12
table open cache size (5.1+): 400.00
rate of table open: 53.85 per hour
% open files: 5.18
rate of open files: 42.60 per hour
Immediate table locks %: 100.00
Table lock wait rate: 0.00 per day
thread cache: 0.00
Total threads created: 559.00
thread cache hit rate %: 1.00
Threads that are slow to launch: 0.00
Slow launch time: 2.00
% connections used: 5.30
Max connections used: 8.00
Max connections limit: 151.00
% aborted connections: 0.36
rate of aborted connections: 1.61 per hour
% aborted clients: 0.00
rate of aborted clients: 0.00 per day
Is InnoDB enabled?: YES
% innoDB log size: 3.91
Number found where operator expected at (eval 140) line 1, near "AUTOeq 0" (#2)
(S syntax) The Perl lexer knows whether to expect a term or an operator.
If it sees what it knows to be a term when it was expecting to see an
operator, it gives you this warning. Usually it indicates that an
operator or delimiter was omitted, such as a semicolon.
(Do you need to predeclare AUTOeq?)
MyISAM concurrent inserts:
RECOMMENDATIONS:
Uptime is less than 1 day, performance tuning may not be accurate
long_query_time is set to 10 seconds or more. This may not be appropriate for your environment.
Enable the slow query log to troubleshoot bad queries.
version less then 5.1, upgrade!
query cache not efficient, consider increasing query_cache_limit.
The query_cache is not turned on. It may be useful to turn it on.
The max size of the result set in the query cache is the default of 1 Mb. Changing this (usually by increasing) may increase efficiency.
There are too many joins without indexes -- this means that joins are doing full table scans.
The rate of reading the first index entry is high; this usually indicates frequent full index scans.
The rate of reading the next table row is high; this indicates many queries are doing full table scans.
Too many intermediate temporary tables are being created; consider increasing sort_buffer_size (sorting), read_rnd_buffer_size (random read buffer, ie, post-sort), read_buffer_size (sequential scan).
MyISAM key buffer (index cache) % used is low. You may need to decrease the size of key_buffer_size, re-examine your tables to see if indexes have been removed, or examine queries and expectations about what indexes are being used.
MyISAM key buffer (index cache) % used is low. You may need to decrease the size of key_buffer_size, re-examine your tables to see if indexes have been removed, or examine queries and expectations about what indexes are being used.
Size of the table cache
Enable the thread cache by setting thread_cache_size>0 for less overhead from new connections to MySQL.
InnoDB log file size is not an appropriate size, in relation to the InnoDB buffer pool. Consider changing either\ninnodb_log_file_size or innodb_buffer_pool_size
Percona Toolkit
El descarregarem de la seva pàgina i instal·larem l'rpm o bé podem optar per una solució "portable" i desempaquetar un tar i executar-ne els scripts de dins.
A la seva [documentació https://www.percona.com/doc/percona-toolkit/LATEST/index.html] s'hi detallen les diverses eines que tenim disponibles. N'hi ha moltes, però la que m'ha cridat l'atenció ha sigut la pt-mysql-summary que ens permet veure sobretot, en comptes d'optimitzar com a tal, els paràmetres que tenim configurats pel SGBD en aquell moment. Un exemple de sortida seria el següent:
# Percona Toolkit MySQL Summary Report #######################
System time | 2018-05-24 15:24:07 UTC (local TZ: CEST +0200)
# Instances ##################################################
Port Data Directory Nice OOM Socket
===== ========================== ==== === ======
0 0
/home/guillem/.local/share/akonadi/db_data/ 0 0 /tmp/akonadi-guillem.8z3Bop/mysql.socket
# MySQL Executable ###########################################
Path to executable | /usr/libexec/mysqld
Has symbols | Yes
# Slave Hosts ################################################
No slaves found
# Report On Port 3306 ########################################
User | root@%
Time | 2018-05-24 17:24:07 (CEST)
Hostname | mediawiki.virtual
Version | 5.5.56-MariaDB MariaDB Server
Built On | Linux x86_64
Started | 2018-05-24 15:03 (up 0+02:21:02)
Databases | 4
Datadir | /var/lib/mysql/
Processes | 1 connected, 1 running
Replication | Is not a slave, has 0 slaves connected
Pidfile | /var/run/mariadb/mariadb.pid (exists)
# Processlist ################################################
Command COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
Query 1 1 0 0
User COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
root 1 1 0 0
Host COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
192.168.56.1 1 1 0 0
db COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
NULL 1 1 0 0
State COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
NULL 1 1 0 0
# Status Counters (Wait 10 Seconds) ##########################
Variable Per day Per second 11 secs
Aborted_connects 40
Access_denied_errors 40
Aria_pagecache_blocks_unused 150000 1
Aria_pagecache_blocks_used 100
Aria_pagecache_read_requests 6000
Aria_pagecache_reads 250
Aria_pagecache_write_requests 450
Bytes_received 125000000 1250 200
Bytes_sent 4500000000 50000 2250
Com_admin_commands 30
Com_begin 22500
Com_change_db 22500
Com_commit 17500
Com_delete 7000
Com_insert 1500
Com_lock_tables 10
Com_replace 15000
Com_select 500000 6
Com_set_option 25000
Com_show_binlogs 20
Com_show_create_db 10
Com_show_create_table 500
Com_show_databases 20
Com_show_engine_status 20
Com_show_fields 500
Com_show_master_status 20
Com_show_plugins 20
Com_show_processlist 20
Com_show_slave_hosts 20
Com_show_slave_status 20
Com_show_status 600
Com_show_storage_engines 10
Com_show_table_status 500
Com_show_tables 10
Com_show_triggers 500
Com_show_variables 15000
Com_unlock_tables 10
Com_update 1500
Connections 25000 1
Created_tmp_disk_tables 1750
Created_tmp_files 60
Created_tmp_tables 20000
Empty_queries 80000
Feature_subquery 60
Feature_timezone 10
Flush_commands 20
Handler_commit 600000 6
Handler_delete 8000
Handler_icp_attempts 400000 4
Handler_icp_match 400000 4
Handler_read_first 5000
Handler_read_key 600000 7
Handler_read_next 70000
Handler_read_prev 6000
Handler_read_rnd 8000
Handler_read_rnd_next 350000 3 40
Handler_rollback 4000
Handler_tmp_update 150
Handler_tmp_write 80000 40
Handler_update 9000
Handler_write 17500
Innodb_adaptive_hash_cells 3000000 35
Innodb_adaptive_hash_hash_searches 450000 5
Innodb_adaptive_hash_heap_buffers 100
Innodb_adaptive_hash_non_hash_searches 3000000 35
Innodb_background_log_sync 50000 1
Innodb_buffer_pool_bytes_data 250000000 3000
Innodb_buffer_pool_pages_flushed 60000
Innodb_buffer_pool_pages_old 6000
Innodb_buffer_pool_read_requests 10000000 125
Innodb_buffer_pool_reads 15000
Innodb_buffer_pool_write_requests 200000 2
Innodb_checkpoint_max_age 80000000 900
Innodb_checkpoint_target_age 80000000 900
Innodb_data_fsyncs 30000
Innodb_data_read 300000000 3500
Innodb_data_reads 17500
Innodb_data_writes 90000 1
Innodb_data_written 2000000000 25000
Innodb_dblwr_pages_written 60000
Innodb_dblwr_writes 1500
Innodb_descriptors_memory 80000
Innodb_dict_tables 600
Innodb_history_list_length 20000
Innodb_ibuf_free_list 50
Innodb_ibuf_merged_inserts 50
Innodb_ibuf_merges 50
Innodb_ibuf_segment_size 70
Innodb_ibuf_size 10
Innodb_log_write_requests 50000
Innodb_log_writes 25000
Innodb_lsn_current 2000000000 22500
Innodb_lsn_flushed 2000000000 22500
Innodb_lsn_last_checkpoint 2000000000 22500
Innodb_master_thread_1_second_loops 15000
Innodb_master_thread_10_second_loops 1250
Innodb_master_thread_background_loops 1000
Innodb_master_thread_main_flush_loops 1000
Innodb_master_thread_sleeps 15000
Innodb_max_trx_id 5000000 60
Innodb_mem_adaptive_hash 25000000 300
Innodb_mem_dictionary 10000000 125
Innodb_mem_total 1500000000 17500
Innodb_mutex_os_waits 500
Innodb_mutex_spin_rounds 17500
Innodb_mutex_spin_waits 600
Innodb_oldest_view_low_limit_trx_id 5000000 60
Innodb_os_log_fsyncs 30000
Innodb_os_log_written 35000000 400
Innodb_pages_created 800
Innodb_pages_read 15000
Innodb_pages_written 60000
Innodb_purge_trx_id 5000000 60
Innodb_read_views_memory 2000
Innodb_row_lock_time 30000
Innodb_row_lock_waits 30
Innodb_rows_deleted 8000
Innodb_rows_inserted 9000
Innodb_rows_read 800000 9
Innodb_rows_updated 9000
Innodb_s_lock_os_waits 1500
Innodb_s_lock_spin_rounds 45000
Innodb_s_lock_spin_waits 1500
Innodb_x_lock_os_waits 125
Innodb_x_lock_spin_rounds 5000
Innodb_x_lock_spin_waits 60
Key_read_requests 600000 6
Key_reads 3000
Key_write_requests 175000 2
Key_writes 40000
Open_table_definitions 900
Opened_files 8000
Opened_table_definitions 600
Opened_tables 1750
Queries 700000 8 3
Questions 700000 8 3
Rows_read 800000 9
Rows_sent 800000 9 40
Rows_tmp_read 90000 1 40
Select_range 8000
Select_scan 22500
Sort_range 175
Sort_rows 8000
Sort_scan 250
Syncs 20
Table_locks_immediate 600000 6
Threads_created 25000 1
Uptime 90000 1 1
# Table cache ################################################
Size | 400
Usage | 50%
# Key Percona Server features ################################
Table & Index Stats | Disabled
Multiple I/O Threads | Enabled
Corruption Resilient | Enabled
Durable Replication | Disabled
Import InnoDB Tables | Disabled
Fast Server Restarts | Disabled
Enhanced Logging | Disabled
Replica Perf Logging | Not Supported
Response Time Hist. | Not Supported
Smooth Flushing | Enabled
HandlerSocket NoSQL | Not Supported
Fast Hash UDFs | Unknown
# Percona XtraDB Cluster #####################################
# Plugins ####################################################
InnoDB compression | ACTIVE
# Query cache ################################################
query_cache_type | ON
Size | 0.0
Usage | 0%
HitToInsertRatio | 0%
# Schema #####################################################
Specify --databases or --all-databases to dump and summarize schemas
# Noteworthy Technologies ####################################
SSL | No
Explicit LOCK TABLES | Yes
Delayed Insert | No
XA Transactions | No
NDB Cluster | No
Prepared Statements | No
Prepared statement count | 0
# InnoDB #####################################################
Version | 5.5.52-MariaDB-38.3
Buffer Pool Size | 128.0M
Buffer Pool Fill | 20%
Buffer Pool Dirty | 0%
File Per Table | OFF
Page Size | 16k
Log File Size | 2 * 5.0M = 10.0M
Log Buffer Size | 8M
Flush Method |
Flush Log At Commit | 1
XA Support | ON
Checksums | ON
Doublewrite | ON
R/W I/O Threads | 4 4
I/O Capacity | 200
Thread Concurrency | 0
Concurrency Tickets | 500
Commit Concurrency | 0
Txn Isolation Level | REPEATABLE-READ
Adaptive Flushing | ON
Adaptive Checkpoint |
Checkpoint Age | 0
InnoDB Queue | 0 queries inside InnoDB, 0 queries in queue
Oldest Transaction | 0 Seconds
History List Len | 2056
Read Views | 1
Undo Log Entries | 0 transactions, 0 total undo, 0 max undo
Pending I/O Reads | 0 buf pool reads, 0 normal AIO, 0 ibuf AIO, 0 preads
Pending I/O Writes | 0 buf pool (0 LRU, 0 flush list, 0 page); 0 AIO, 0 sync, 0 log IO (0 log, 0 chkp); 0 pwrites
Pending I/O Flushes | 0 buf pool, 0 log
Transaction States | 1xnot started
# MyISAM #####################################################
Key Cache | 128.0M
Pct Used | 20%
Unflushed | 0%
# Security ###################################################
Users | 3 users, 0 anon, 0 w/o pw, 0 old pw
Old Passwords | OFF
# Encryption #################################################
No keyring plugins found
# Binary Logging #############################################
# Noteworthy Variables #######################################
Auto-Inc Incr/Offset | 1/1
default_storage_engine | InnoDB
flush_time | 0
init_connect |
init_file |
sql_mode |
join_buffer_size | 128k
sort_buffer_size | 2M
read_buffer_size | 128k
read_rnd_buffer_size | 256k
bulk_insert_buffer | 0.00
max_heap_table_size | 16M
tmp_table_size | 16M
max_allowed_packet | 1M
thread_stack | 288k
log | OFF
log_error | /var/log/mariadb/mariadb.log
log_warnings | 1
log_slow_queries | OFF
log_queries_not_using_indexes | OFF
log_slave_updates | OFF
# Configuration File #########################################
Config File | /etc/my.cnf
[client-server]
[mysqld]
symbolic-links = 0
# Memory management library ##################################
grep: /proc/1162/environ: Permission denied
jemalloc is not enabled in mysql config for process with id 1162
grep: /proc/1162/environ: Permission denied
jemalloc is not enabled in mysql config for process with id 1162
# The End ####################################################
Aquest script, com he dit abans, ens permet llistar paràmetres referents al MariaDB que està corrent a la meva màquina que allotja la MediaWiki. L'avantatge és que es llista de manera "llegible" per una persona i permet fer un diagnòstic si veiessim, per exemple, que aquell servidor no tira bé o dóna problemes.
Conclusions
Aquests scripts els he executat sobre la màquina virtual on hi tinc la Mediawiki funcionant, perquè no tenia gaire sentit fer-ho a la màquina on he instal·lat el Moodle en les pràctiques anteriors. Això ho he fet pensant que seria interessant veure el resultat d'aquests scripts en un SGBD que hagi estat corrent (interrompudament) durant un període de temps llarg i que hagi tingut activitat; tot i això, no han sortit paràmetres estranys ni mal configurats segons els scripts. Com a molt es pot veure que el Tuning Primer notifica un paràmetre referent a la memòria:
(...) MEMORY USAGE Max Memory Ever Allocated : 294 M Configured Max Per-thread Buffers : 419 M Configured Max Global Buffers : 272 M Configured Max Memory Limit : 691 M Physical Memory : 487 M Max memory limit exceeds 90% of physical memory (...)
Veiem que la memòria màxima configurada és igual a 691 MB, mentre que la memòria física que té la màquina és de 487 MB. Llavors l'avís és que el lñimit màxim de memòria és superior al 90% de la memòria RAM de la màquina. Aquest paràmetre es devia quedar així al moment de la instal·lació perquè en aquell moment la màquina tenia 1 GB de RAM però vaig creure convenient reduir recursos perquè no és una màquina que demani molta potència ni molta memòria per a mantenir la Mediawiki corrent; i per això actualment té 512 MB assignats. Això fa incoherent que el valor màxim de memòria que pot utilitzar el servidor sigui superior a la memòria disponible i s'hauria d'ajustar. Veient que la memòria màxima alocada per al servidor ha sigut d'aproximadament 300 MB, i tenint 487 MB en total podria modificar aquest paràmetre i deixar-lo en un terme mig de 350 MB.
