再谈shared_buffers-数据库管理、开发实践专场（27页）.pdf

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1、刘阳明shared_buffers“Sets the amount of memory the database server uses for shared memory buffers.The default is typically 128 megabytes(128MB),but might be less if your kernel settings will not support it(as determined during initdb).This setting must be at least 128 kilobytes.(Non-default values of B

2、LCKSZ change the minimum.)However,settings significantly higher than the minimum are usually needed for good performance.This parameter can only be set at server start.If you have a dedicated database server with 1GB or more of RAM,a reasonable starting value for shared_buffers is 25%of the memory i

3、n your system.There are some workloads where even larger settings for shared_buffers are effective,but because PostgreSQL also relies on the operating system cache,it is unlikely that an allocation of more than 40%of RAM to shared_buffers will work better than a smaller amount.Larger settings for sh

4、ared_buffers usually require a corresponding increase in max_wal_size,in order to spread out the process of writing large quantities of new or changed data over a longer period of time.On systems with less than 1GB of RAM,a smaller percentage of RAM is appropriate,so as to leave adequate space for t

5、he operating system.”Why shared_buffers 25%40%?“PostgreSQL also relies on the operating system cache”“Larger settings for shared_buffers usually require a corresponding increase in max_wal_size,in order to spread out the process of writing large quantities of new or changed data over a longer period

6、 of time.”Why shared_buffers 25%40%?“PostgreSQL also relies on the operating system cache”Page cache可以看做多进程架构的应用系统的一种共享数据的cache“Larger settings for shared_buffers usually require a corresponding increase in max_wal_size,in order to spread out the process of writing large quantities of new or changed