vm.dirty_ratio和vm.dirty_background_ratio之间的区别? [英] Difference between vm.dirty_ratio and vm.dirty_background_ratio?

问题描述

我目前正在尝试使用/proc/sys/vm中的内核参数，尤其是dirty_ratio和dirty_background_ratio.

I'm currently experimenting with the kernel parameters found in /proc/sys/vm, especially dirty_ratio and dirty_background_ratio.

内核文档对这两者都有以下说明:

The kernel doc has the following explanations for both:

dirty_background_ratio

dirty_background_ratio

包含包含可用页面的总可用内存的百分比 和可回收页面，即后台内核所在的页面数 刷新器线程将开始写出脏数据.

Contains, as a percentage of total available memory that contains free pages and reclaimable pages, the number of pages at which the background kernel flusher threads will start writing out dirty data.

和

dirty_ratio

dirty_ratio

包含包含可用页面的总可用内存的百分比 和可回收页面，指的是要处理的页面数 生成磁盘写操作本身将开始写脏数据.

Contains, as a percentage of total available memory that contains free pages and reclaimable pages, the number of pages at which a process which is generating disk writes will itself start writing out dirty data.

在我的Linux系统上，dirty_background_ratio是10，而dirty_ratio是20.因此，如果我的已用内存达到10％，内核将开始回写，并且永远不会达到20％.

On my linux system dirty_background_ratio is 10 and dirty_ratio is 20. I understand that the difference is, who the dirty data writes. So if my used memory reaches 10% the kernel starts writing back and 20% should never be reached.

我现在的问题是:dirty_background_ratio和dirty_ratio的较高值有什么含义吗?还是仅是较低的值是谁?"的问题?

My question now is: Has the higher value of dirty_background_ratio and dirty_ratio any meaning or is it just a matter of "what is the lower value and who has it"?

推荐答案

dirty_background_ratio和dirty_ratio的较高值是否有意义?或者仅仅是较低的值是谁，谁拥有它"的问题?

Has the higher value of dirty_background_ratio and dirty_ratio any meaning or is it just a matter of "what is the lower value and who has it"?

更简单的话:

vm.dirty_background_ratio 是系统内存的百分比，当该内存变脏时，系统可以开始将数据写入磁盘.

vm.dirty_background_ratio is the percentage of system memory which when dirty then system can start writing data to the disks.

vm.dirty_ratio 是系统内存的百分比，当该内存脏时，执行写操作的进程将阻止并将脏页写出到磁盘.

vm.dirty_ratio is percentage of system memory which when dirty, the process doing writes would block and write out dirty pages to the disks.

此可调参数取决于系统的运行状况，如果运行大型数据库，则建议将这些值保持较低，以避免I/O瓶颈和系统负载增加时.

This tunable depends on what your system running, if you run large database its recommend to keep these values low to avoid I/O bottle-necks and when the system load increases.

例如:

vm.dirty_background_ratio=10
vm.dirty_ratio=15

在此示例中，当脏页超过vm.dirty_background_ratio=10时，将启动I/O，即开始刷新/写入磁盘.当脏页总数超过vm.dirty_ratio=15时，所有写入将被阻止，直到某些脏页被写入磁盘为止.您可以将vm.dirty_ratio=15视为上限.

In this example when the dirty pages exceed vm.dirty_background_ratio=10 I/O starts, i.e they start getting flushed / written to the disk. When total number of dirty pages exceed vm.dirty_ratio=15 all writes get blocked until some of the dirty pages get written to disk. You can think of the vm.dirty_ratio=15 as the upper limit.

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