Linux中对MySQL优化实例详解
<p><strong>Linux中对MySQL优化实例详解</strong></p>
<p>
vim /etc/my.cnf以下只列出my.cnf文件中段落中的内容，其他段落内容对MySQL运行性能影响甚微，因而姑且忽略。</p>
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<code class="bash plain">port = 3306</code>
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<code class="bash plain">serverid = 1</code>
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<code class="bash plain">socket = </code><code class="bash plain">/tmp/mysql</code><code class="bash plain">.sock</code>
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<code class="bash plain">skip-locking</code>
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避免MySQL的外部锁定，减少出错几率增强稳定性。</p>
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<code class="bash plain">skip-name-resolve</code>
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禁止MySQL对外部连接进行DNS解析，使用这一选项可以消除MySQL进行DNS解析的时间。但需要注意，如果开启该选项，则所有远程主机连接授权都要使用IP地址方式，否则MySQL将无法正常处理连接请求！</p>
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<code class="bash plain">back_log = 384</code>
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back_log参数的值指出在MySQL暂时停止响应新请求之前的短时间内多少个请求可以被存在堆栈中。如果系统在一个短时间内有很多连接，则需要增大该参数的值，该参数值指定到来的TCP/IP连接的侦听队列的大小。不同的操作系统在这个队列大小上有它自己的限制。试图设定back_log高于你的操作系统的限制将是无效的。默认值为50。对于Linux系统推荐设置为小于512的整数。</p>
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<code class="bash plain">key_buffer_size = 256M</code>
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key_buffer_size指定用于索引的缓冲区大小，增加它可得到更好的索引处理性能。对于内存在4GB左右的服务器该参数可设置为256M或384M。注意：该参数值设置的过大反而会是服务器整体效率降低！</p>
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<code class="bash plain">max_allowed_packet = 4M</code>
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<code class="bash plain">thread_stack = 256K</code>
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<code class="bash plain">table_cache = 128K</code>
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<code class="bash plain">sort_buffer_size = 6M</code>
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查询排序时所能使用的缓冲区大小。注意：该参数对应的分配内存是每连接独占，如果有100个连接，那么实际分配的总共排序缓冲区大小为100 × 6 ＝ 600MB。所以，对于内存在4GB左右的服务器推荐设置为6-8M。</p>
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<code class="bash plain">read_buffer_size = 4M</code>
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读查询操作所能使用的缓冲区大小。和sort_buffer_size一样，该参数对应的分配内存也是每连接独享。</p>
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<code class="bash plain">join_buffer_size = 8M</code>
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联合查询操作所能使用的缓冲区大小，和sort_buffer_size一样，该参数对应的分配内存也是每连接独享。</p>
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<code class="bash plain">myisam_sort_buffer_size = 64M</code>
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<code class="bash plain">table_cache = 512</code>
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<code class="bash plain">thread_cache_size = 64</code>
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<code class="bash plain">query_cache_size = 64M</code>
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指定MySQL查询缓冲区的大小。可以通过在MySQL控制台观察，如果Qcache_lowmem_prunes的值非常大，则表明经常出现缓冲不够的情况；如果Qcache_hits的值非常大，则表明查询缓冲使用非常频繁，如果该值较小反而会影响效率，那么可以考虑不用查询缓冲；Qcache_free_blocks，如果该值非常大，则表明缓冲区中碎片很多。</p>
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<code class="bash plain">tmp_table_size = 256M</code>
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<code class="bash plain">max_connections = 768</code>
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指定MySQL允许的最大连接进程数。如果在访问论坛时经常出现Too ManyConnections的错误提示，则需要增大该参数值。</p>
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<code class="bash plain">max_connect_errors = 10000000</code>
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<code class="bash plain">wait_timeout = 10</code>
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指定一个请求的最大连接时间，对于4GB左右内存的服务器可以设置为5-10。</p>
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<code class="bash plain">thread_concurrency = 8</code>
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该参数取值为服务器逻辑CPU数量*2，在本例中，服务器有2颗物理CPU，而每颗物理CPU又支持H.T超线程，所以实际取值为4*2=8</p>
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<code class="bash plain">skip-networking</code>
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开启该选项可以彻底关闭MySQL的TCP/IP连接方式，如果WEB服务器是以远程连接的方式访问MySQL数据库服务器则不要开启该选项！否则将无法正常连接！</p>
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<code class="bash plain">table_cache=1024</code>
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物理内存越大,设置就越大.默认为2402,调到512-1024最佳</p>
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<code class="bash plain">innodb_additional_mem_pool_size=4M</code>
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默认为2M</p>
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<code class="bash plain">innodb_flush_log_at_trx_commit=1</code>
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设置为0就是等到innodb_log_buffer_size列队满后再统一储存,默认为1</p>
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<code class="bash plain">innodb_log_buffer_size=2M</code>
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默认为1M</p>
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<code class="bash plain">innodb_thread_concurrency=8</code>
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你的服务器CPU有几个就设置为几,建议用默认一般为8</p>
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<code class="bash plain">key_buffer_size=256M</code>
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<code class="bash comments">#默认为218，调到128最佳</code>
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<code class="bash plain">tmp_table_size=64M </code>
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<code class="bash comments">#默认为16M，调到64-256最挂</code>
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<code class="bash plain">read_buffer_size=4M </code>
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<code class="bash comments">#默认为64K</code>
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<code class="bash plain">read_rnd_buffer_size=16M </code>
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<code class="bash comments">#默认为256K</code>
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<code class="bash plain">sort_buffer_size=32M </code>
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<code class="bash comments">#默认为256K</code>
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<code class="bash plain">thread_cache_size=120 </code>
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<code class="bash comments">#默认为60</code>
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<code class="bash plain">query_cache_size=32M </code>
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<strong>值得注意的是： </strong></p>
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很多情况需要具体情况具体分析</p>
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一、如果Key_reads太大，则应该把my.cnf中Key_buffer_size变大，保持Key_reads/Key_read_requests至少1/100以上，越小越好。</p>
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二、如果Qcache_lowmem_prunes很大，就要增加Query_cache_size的值。</p>
<p>
感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！</p>
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原文链接：http://blog.csdn.net/enterys/article/details/70172369</p>
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