Thesql using 80% cpu usage

MySQLoptimization

my mysql is using about 70-80% every time of cpu and about 5% memory, and many times when high traffic, websites takes too long to load

could someone help me?

my server is 8 core with 32gb ram, im using centos 6.9 with cpanel/cloudlinux

here is my my.cnf and mysqltuner log

[mysqld]

innodb_file_per_table=1

local-infile=0

tmpdir =/dev/shm

max_connections = 1024

max_user_connections=650

key_buffer_size = 1024M

myisam_sort_buffer_size = 64M

#default-storage-engine=MyISAM

join_buffer_size = 1M

read_buffer_size = 1M

sort_buffer_size = 256K

thread_cache_size = 384

wait_timeout = 20

connect_timeout = 10

tmp_table_size = 64M

max_heap_table_size = 64M

max_allowed_packet = 64M

net_buffer_length = 16384

max_connect_errors = 10

thread_concurrency = 16

concurrent_insert = 2

read_rnd_buffer_size = 786432

bulk_insert_buffer_size = 8M

query_cache_limit = 7M

query_cache_size = 64M

query_cache_type = 1

query_prealloc_size = 262144

query_alloc_block_size = 65536

transaction_alloc_block_size = 8192

transaction_prealloc_size = 4096

max_write_lock_count = 16

innodb_buffer_pool_size=8G #75 % of RAM

innodb_flush_log_at_trx_commit=2

innodb_thread_concurrency=8 # of cpus

innodb_flush_method=O_DIRECT


[mysqld_safe]

open_files_limit = 8192


[mysqldump]

quick

max_allowed_packet = 16M


[myisamchk]

key_buffer = 384M

sort_buffer = 384M

read_buffer = 256M

/////////////////////////////

and here is mysqltuner output

——– Performance Metrics ———————————————————————–

[--] Up for: 2d 3h 25m 54s (23M q [127.290 qps], 468K conn, TX: 138G, RX: 7G)

[--] Reads / Writes: 89% / 11%

[--] Binary logging is disabled

[--] Physical Memory : 31.3G

[--] Max MySQL memory : 12.9G

[--] Other process memory: 3.9G

[--] Total buffers: 9.1G global + 3.2M per thread (1024 max threads)

[--] P_S Max memory usage: 555M

[--] Galera GCache Max memory usage: 0B

[OK] Maximum reached memory usage: 10.0G (31.77% of installed RAM)

[OK] Maximum possible memory usage: 12.9G (41.28% of installed RAM)

[OK] Overall possible memory usage with other process is compatible with memory available

[OK] Slow queries: 0% (5K/23M)

[OK] Highest usage of available connections: 8% (85/1024)

[OK] Aborted connections: 0.55% (2598/468725)

[!!] name resolution is active : a reverse name resolution is made for each new connection and can reduce performance

[!!] Query cache may be disabled by default due to mutex contention.

[OK] Query cache efficiency: 61.7% (12M cached / 19M selects)

[!!] Query cache prunes per day: 1008253

[OK] Sorts requiring temporary tables: 0% (2K temp sorts / 34M sorts)

[!!] Joins performed without indexes: 150075

[!!] Temporary tables created on disk: 52% (577K on disk / 1M total)

[OK] Thread cache hit rate: 99% (85 created / 468K connections)

[!!] Table cache hit rate: 1% (2K open / 102K opened)

[OK] Open file limit used: 24% (1K/8K)

[OK] Table locks acquired immediately: 99% (38M immediate / 38M locks)


-------- Performance schema ------------------------------------------------------------------------

[--] Memory used by P_S: 555.4M

[--] Sys schema isn't installed.


-------- ThreadPool Metrics ------------------------------------------------------------------------

[--] ThreadPool stat is disabled.


-------- MyISAM Metrics ----------------------------------------------------------------------------

[!!] Key buffer used: 26.8% (287M used / 1B cache)

[OK] Key buffer size / total MyISAM indexes: 1.0G/1.5G

[OK] Read Key buffer hit rate: 100.0% (2B cached / 572K reads)

[!!] Write Key buffer hit rate: 30.1% (2M cached / 899K writes)


-------- InnoDB Metrics ----------------------------------------------------------------------------

[--] InnoDB is enabled.

[--] InnoDB Thread Concurrency: 8

[OK] InnoDB File per table is activated

[OK] InnoDB buffer pool / data size: 8.0G/1.2G

[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (1.171875 %): 48.0M * 2/8.0G should be equal 25%

[OK] InnoDB buffer pool instances: 8

[--] InnoDB Buffer Pool Chunk Size not used or defined in your version

[OK] InnoDB Read buffer efficiency: 100.00% (786635092 hits/ 786673138 total)

[!!] InnoDB Write Log efficiency: 51.42% (236640 hits/ 460226 total)

[OK] InnoDB log waits: 0.00% (0 waits / 223586 writes)


-------- AriaDB Metrics ----------------------------------------------------------------------------

[--] AriaDB is disabled.


-------- TokuDB Metrics ----------------------------------------------------------------------------

[--] TokuDB is disabled.


-------- XtraDB Metrics ----------------------------------------------------------------------------

[--] XtraDB is disabled.


-------- RocksDB Metrics ---------------------------------------------------------------------------

[--] RocksDB is disabled.


-------- Spider Metrics ----------------------------------------------------------------------------

[--] Spider is disabled.


-------- Connect Metrics ---------------------------------------------------------------------------

[--] Connect is disabled.


-------- Galera Metrics ----------------------------------------------------------------------------

[--] Galera is disabled.


-------- Replication Metrics -----------------------------------------------------------------------

[--] Galera Synchronous replication: NO

[--] No replication slave(s) for this server.

[--] This is a standalone server.


-------- Recommendations ---------------------------------------------------------------------------

General recommendations:

Run OPTIMIZE TABLE to defragment tables for better performance

OPTIMIZE TABLE `modsec`.`hits`; -- can free 382.777297973633 MB

Total freed space after theses OPTIMIZE TABLE : 382.777297973633 Mb

Set up a Secure Password for user@host ( SET PASSWORD FOR 'user'@'SpecificDNSorIp' = PASSWORD('secure_password'); )
 Restrict Host for user@% to user@SpecificDNSorIp

Configure your accounts with IP or subnets only, then update your
configuration with skip-name-resolve=1

Adjust your join queries to always utilize indexes

When making adjustments, make tmp_table_size/max_heap_table_size equal

Reduce your SELECT DISTINCT queries which have no LIMIT clause

Increase table_open_cache gradually to avoid file descriptor limits

Read this before increasing table_open_cache over 64: table_cache
negative scalability

Beware that open_files_limit (8192) variable

should be greater than table_open_cache (2000)

Consider installing Sys schema from GitHub – mysql/mysql-sys: The
MySQL sys schema

Read this before changing innodb_log_file_size and/or
innodb_log_files_in_group: MySQL :: MySQL 5.7 Reference Manual ::
14.7.2 Changing the Number or Size of InnoDB Redo Log Files

Variables to adjust:

query_cache_size (=0)

query_cache_type (=0)

query_cache_size (> 64M)

join_buffer_size (> 1.0M, or always use indexes with joins)

tmp_table_size (> 64M)

max_heap_table_size (> 64M)

table_open_cache (> 2000)

innodb_log_file_size should be (=1G) if possible, so InnoDB total log files size equals to 25% of buffer pool size.

Best Answer

"You can't tune your way out of a performance problem."

The Query Cache may be part of the problem. It is running moderately efficiently, but there are a lot of prunes -- 12/second. Prunes are costly.

MyISAM may be part of the problem. You should convert to InnoDB.

While some of mysqltuner's and Wilson's suggestions will help some, the real problem with high CPU is almost always poor indexes or poorly formatted queries.

Turn on the slowlog with long_query_time 1; wait a day; run pt-query-digest or mysqldumpslow -s t to find the 'worst' queries. Then has for help in speeding them up. More.

This may be the most important tuner comment in your case:

[!!] Temporary tables created on disk: 52% (577K on disk / 1M total)

That's about 6/second, about the 90th percentile compared to other servers. Are you running on Windows? What version of MySQL?

Do you use TEXT for columns that could be suitably sized VARCHAR(...)? Do you use SELECT * when you need only smaller list of columns? Both of these can lead to tmp tables on disk.

Efficiency in many:many schema.

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Mysql – How to debug a db memory-leak causing thesql to go before it’s own limits

...even surpassing it's theorically maximum possible allocation.

[OK] Maximum possible memory usage: 7.3G (46% of installed RAM)

There is not actually a way to calculate maximum possible memory usage for MySQL, because there is no cap on the memory it can request from the system.

The calculation done by mysqltuner.pl is only an estimate, based on a formula that doesn't take into account all possible variables, because if all possible variables were taken into account, the answer would always be "infinite." It's unfortunate that it's labeled this way.

Here is my theory on what's contributing to your excessive memory usage:

thread_cache_size       = 128

Given that your max_connections is set to 200, the value of 128 for thread_cache_size seems far too high. Here's what makes me think this might be contributing to your problem:

When a thread is no longer needed, the memory allocated to it is released and returned to the system unless the thread goes back into the thread cache. In that case, the memory remains allocated.

^{http://dev.mysql.com/doc/refman/5.6/en/memory-use.html}

If your workload causes even an occasional client thread to require a large amount of memory, those threads may be holding onto that memory, then going back to the pool and sitting around, continuing to hold on to memory they don't technically "need" any more, on the premise that holding on to the memory is less costly than releasing it if you're likely to need it again.

I think it's worth a try to do the following, after first making a note of how much memory MySQL is using at the moment.

Note how many threads are currently cached:

mysql> show status like 'Threads_cached';
+----------------+-------+
| Variable_name  | Value |
+----------------+-------+
| Threads_cached | 9     |
+----------------+-------+
1 row in set (0.00 sec)

Next, disable the thread cache.

mysql> SET GLOBAL thread_cache_size = 0;

This disables the thread cache, but the cached threads will stay in the pool until they're used one more time. Disconnect from the server, then reconnect and repeat.

mysql> show status like 'Threads_cached';

Continue disconnecting, reconnecting, and checking until the counter reaches 0.

Then, see how much memory MySQL is holding.

You may see a decrease, possibly significant, and then again you may not. I tested this on one of my systems, which had 9 threads in the cache. Once those threads had all been cleared out of the cache, the total memory held by MySQL did decrease... not by much, but it does illustrate that threads in the cache do release at least some memory when they are destroyed.

If you see a significant decrease, you may have found your problem. If you don't, then there's one more thing that needs to happen, and how quickly it can happen depends on your environment.

If the theory holds that the other threads -- the ones currently servicing active client connections -- have significant memory allocated to them, either because of recent work in their current client session or because of work requiring a lot of memory that was done by another connection prior to them languishing in the pool, then you won't see all of the potential reduction in memory consumption until those threads are allowed to die and be destroyed. Presumably your application doesn't hold them forever, but how long it will take to know for sure whether there's a difference will depend on whether you have the option of cycling your application (dropping and reconnecting the client threads) or if you'll have to just wait for them to be dropped and reconnected over time on their own.

But... it seems like a worthwhile test. You should not see a substantial performance penalty by setting thread_cache_size to 0. Fortunately, thread_cache_size is a dynamic variable, so you can freely change it with the server running.

Mysql – The total number of locks exceeds the lock table size, even after increasing buffer pool size

Try this in my.cnf file,

[mysqld] innodb_buffer_pool_size = 80M

And you need to restart the Workbench as well as the Sql service.

Best Answer

Related Solutions

Mysql – How to debug a db memory-leak causing thesql to go before it’s own limits

Mysql – The total number of locks exceeds the lock table size, even after increasing buffer pool size

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