Hi,

I've notice some up's and down's in the load average but I con't find anything strange in the logs!

This is a 768 linode wgere I run a vB+vBseo board 250/300 users online.

I don'd find any relations between the load jumps and any other processes like backups, mysqldump, most users onlie, etc.

I use nginx proxying to apache and mysql:

Timeout 50
KeepAlive Off
MaxKeepAliveRequests 100
KeepAliveTimeout 5

<IfModule mpm_prefork_module>
StartServers 3
MinSpareServers 3
MaxSpareServers 3
MaxClients 25
MaxRequestsPerChild 100
</IfModule>

Mysql:

[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /home/mysql
tmpdir = /tmp
language = /usr/share/mysql/english
bind-address = 127.0.0.1
myisam-recover = BACKUP
skip-innodb
back_log = 50
max_connections = 50
key_buffer_size = 64M
myisam_sort_buffer_size = 64M
join_buffer_size = 1M
read_buffer_size = 1M
sort_buffer_size = 2M
table_open_cache = 16000
table_definition_cache = 8000
thread_cache_size = 144
wait_timeout = 3600
connect_timeout = 10
tmp_table_size = 32M
max_heap_table_size = 32M
max_allowed_packet = 32M
net_buffer_length = 16384
max_connect_errors = 100000
thread_concurrency = 4
concurrent_insert = 2
table_lock_wait_timeout = 30
read_rnd_buffer_size = 786432
bulk_insert_buffer_size = 8M
query_cache_limit = 1M
query_cache_size = 48M
query_cache_type = 1
query_prealloc_size = 262144
query_alloc_block_size = 65536
transaction_alloc_block_size = 8192
transaction_prealloc_size = 4096
default-storage-engine = MyISAM
max_write_lock_count = 4
#slow_query_log = 1
#slow_query_log_file = /var/log/mysql/mysql-slow.log
#long_query_time = 3
log-error = /var/log/mysql/mysql-error.log
low_priority_updates=1

[mysqld_safe]
nice = -5
open_files_limit = 8192

[mysqldump]
quick
max_allowed_packet = 16M

[myisamchk]
key_buffer_size = 64M
sort_buffer_size = 16M
read_buffer_size = 16M
write_buffer_size = 16M

[mysqlhotcopy]
interactive-timeout





Where and what should I start looking?

Thanks

Since you have realllly low cpu usage, it doesn't appear to be a cpu problem. Any process which is waiting for data from the disk still counts towards load even if the cpu is doing squat so my guess is those spokes are due to io_wait. Check your mysql slow log, it might show the culprit.

Hi,

Theres only one spike in slow logs in it's default configuration:

That last graph is dated before the ones you were listing do you have a recent one?

Sorry ...

Wast in the cache. Here the new one's:

Your load spikes match up with your mysql threads, try installing and running http://blog.mysqltuner.com/ mysqltuner and see what it says (if you need help interpreting just post here)

Hello,

Here is mysqltuner results:

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.1.37-1ubuntu5.4
[OK] Operating on 32-bit architecture with less than 2GB RAM

-------- Storage Engine Statistics -------------------------------------------
[--] Status: -Archive -BDB -Federated -InnoDB -ISAM -NDBCluster 
[--] Data in MyISAM tables: 236M (Tables: 788)
[--] Data in MEMORY tables: 1M (Tables: 3)
[!!] Total fragmented tables: 17

-------- Performance Metrics -------------------------------------------------
[--] Up for: 12d 20h 46m 5s (8M q [7.337 qps], 572K conn, TX: 2B, RX: 2B)
[--] Reads / Writes: 72% / 28%
[--] Total buffers: 144.0M global + 4.9M per thread (50 max threads)
[OK] Maximum possible memory usage: 390.9M (52% of installed RAM)
[OK] Slow queries: 0% (0/8M)
[OK] Highest usage of available connections: 22% (11/50)
[OK] Key buffer size / total MyISAM indexes: 64.0M/51.0M
[OK] Key buffer hit rate: 99.5% (167M cached / 796K reads)
[OK] Query cache efficiency: 64.1% (3M cached / 6M selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (1 temp sorts / 712K sorts)
[OK] Temporary tables created on disk: 16% (29K on disk / 182K total)
[OK] Thread cache hit rate: 99% (11 created / 572K connections)
[!!] Table cache hit rate: 0% (186 open / 18K opened)
[OK] Open file limit used: 1% (324/32K)
[OK] Table locks acquired immediately: 99% (5M immediate / 5M locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    Enable the slow query log to troubleshoot bad queries
    Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
    table_cache (> 16000)

... and tuning-primer:

   -- MYSQL PERFORMANCE TUNING PRIMER --
        - By: Matthew Montgomery -

MySQL Version 5.1.37-1ubuntu5.4 i486

Uptime = 12 days 20 hrs 47 min 38 sec
Avg. qps = 7
Total Questions = 8156558
Threads Connected = 1

Server has been running for over 48hrs.
It should be safe to follow these recommendations

To find out more information on how each of these
runtime variables effects performance visit:
http://dev.mysql.com/doc/refman/5.1/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 8156579 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/5.1/en/point-in-time-recovery.html

WORKER THREADS
Current thread_cache_size = 144
Current threads_cached = 10
Current threads_per_sec = 0
Historic threads_per_sec = 0
Your thread_cache_size is fine

MAX CONNECTIONS
Current max_connections = 50
Current threads_connected = 1
Historic max_used_connections = 11
The number of used connections is 22% of the configured maximum.
Your max_connections variable seems to be fine.

No InnoDB Support Enabled!

MEMORY USAGE
Max Memory Ever Allocated : 166 M
Configured Max Per-thread Buffers : 246 M
Configured Max Global Buffers : 112 M
Configured Max Memory Limit : 358 M
Physical Memory : 751 M
Max memory limit seem to be within acceptable norms

KEY BUFFER
Current MyISAM index space = 51 M
Current key_buffer_size = 64 M
Key cache miss rate is 1 : 209
Key buffer free ratio = 67 %
Your key_buffer_size seems to be fine

QUERY CACHE
Query cache is enabled
Current query_cache_size = 48 M
Current query_cache_used = 19 M
Current query_cache_limit = 1 M
Current Query cache Memory fill ratio = 41.39 %
Current query_cache_min_res_unit = 4 K
MySQL won't cache query results that are larger than query_cache_limit in size

SORT OPERATIONS
Current sort_buffer_size = 2 M
Current read_rnd_buffer_size = 768 K
Sort buffer seems to be fine

JOINS
Current join_buffer_size = 1.00 M
You have had 374 queries where a join could not use an index properly
You should enable "log-queries-not-using-indexes"
Then look for non indexed joins in the slow query log.
If you are unable to optimize your queries you may want to increase your
join_buffer_size to accommodate larger joins in one pass.

Note! This script will still suggest raising the join_buffer_size when
ANY joins not using indexes are found.

OPEN FILES LIMIT
Current open_files_limit = 32060 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 = 16000 tables
Current table_definition_cache = 8000 tables
You have a total of 814 tables
You have 857 open tables.
The table_cache value seems to be fine

TEMP TABLES
Current max_heap_table_size = 32 M
Current tmp_table_size = 32 M
Of 153530 temp tables, 16% were created on disk
Created disk tmp tables ratio seems fine

TABLE SCANS
Current read_buffer_size = 1 M
Current table scan ratio = 189 : 1
read_buffer_size seems to be fine

TABLE LOCKING
Current Lock Wait ratio = 1 : 13844
Your table locking seems to be fine

eek! your slow query log time is 10 seconds I didn't notice that.
Uncomment these lines

#slow_query_log = 1
#slow_query_log_file = /var/log/mysql/mysql-slow.log
#long_query_time = 3

and add

log_queries_not_using_indexes=1

Let it run for a couple of days then check the slow query log again.

Also set up a cron that runs

mysqlcheck -A -o -a -u <mysqluser>

where mysql user is a user that has access to the databases. It'll analyse and optimise all databases.

Hello,

Here are the new results ...

 >>  MySQLTuner 1.0.1 - Major Hayden <major@mhtx.net>
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
 >>  Run with '--help' for additional options and output filtering
Please enter your MySQL administrative login: root
Please enter your MySQL administrative password: 

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.1.37-1ubuntu5.4-log
[OK] Operating on 32-bit architecture with less than 2GB RAM

-------- Storage Engine Statistics -------------------------------------------
[--] Status: -Archive -BDB -Federated -InnoDB -ISAM -NDBCluster 
[--] Data in MyISAM tables: 249M (Tables: 989)
[--] Data in MEMORY tables: 1M (Tables: 3)
[OK] Total fragmented tables: 0

-------- Performance Metrics -------------------------------------------------
[--] Up for: 1d 14h 19m 42s (1M q [10.609 qps], 99K conn, TX: 2B, RX: 515M)
[--] Reads / Writes: 71% / 29%
[--] Total buffers: 144.0M global + 4.9M per thread (50 max threads)
[OK] Maximum possible memory usage: 390.9M (52% of installed RAM)
[!!] Slow queries: 7% (110K/1M)
[OK] Highest usage of available connections: 26% (13/50)
[OK] Key buffer size / total MyISAM indexes: 64.0M/52.1M
[OK] Key buffer hit rate: 99.6% (32M cached / 131K reads)
[OK] Query cache efficiency: 66.0% (734K cached / 1M selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 113K sorts)
[OK] Temporary tables created on disk: 14% (4K on disk / 27K total)
[OK] Thread cache hit rate: 99% (13 created / 99K connections)
[!!] Table cache hit rate: 1% (91 open / 6K opened)
[OK] Open file limit used: 0% (137/32K)
[OK] Table locks acquired immediately: 99% (966K immediate / 967K locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
    Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
    table_cache (> 16000)

Well there's your problem up to 3 slow queries a second, you need to optimise your queries, especially since slow query time is set to 3 seconds which is a really long time on the web, check your slow query log, you probably need to add some indexes in somewhere, also check out the mysql EXPLAIN statement.