为什么我的proftpd使系统负载达到90%以上？

mgx0018

我的电脑为P4 2.0G 256MDDR 用Debian+proftpd,DMA已打开，单人下载时多大流量都没问题，可是超过3人下载时，系统负载就超过80%，多于5 个人就接近100%了，而它们的总流量和一个下载时差不多，这是为什么，是不是我什么选项没设置，请各位高手解释一下，先谢了。

hgkrt

你流量多大??100MB/10MB还是1MB..

一般系统负载和流量有关系..越大,对CPU的负载就越大..

我的proftpd,15个用户,和1个用户的时候,负载没多大变化...95%空闲...

mgx0018

我的流量是2MB，对每个用户限速200k，两个没问题，可是多于4个负载就达到80%以上，这是为什么？

sfatsdu

If you limit the download speed, then proftpd will not use "sendfile" systemcall to reduce the load, in fact, that will trash your system very hard.But since your box is fast, it should not be a issue.

Another reason is the files users are downloading are not continuous, this will cause harddistk move the arm ,then reduce the performance.Does your disk trash when several users are downloading?
Use "top" to see which process is eating up the CPU?

mgx0018

用户下载的大部份是电影，是连续的，我用top看了一下，每个proftpd进程的%CPU为2.0-3.0之间，当有4个以上进程时，上边的CPU(s)的wa已达到80%-90%，播放音乐都时断时续。是不是我系统有什么没设置好？

sfatsdu

4*2% <=10% Proftpd seems doesn't eat up many CPU.
So which is the real cpu hog? can you grab it from the top result?It's hard to imagine without sit before your box.Are you using X? or the updatedb is running?try to work under a console.
About the harddisk, maybe your movie files are continuous, but when different users are downloading different files, it will still cause the disk arm to move here and there, and trash the disk.

mgx0018

正常情况下，普通PC在保持负载60%情况下，能承受多少人同时下载呀？我的硬盘是160G的，主板是845E，用的Debian/Linux，kernel-2.6.0-test8,请问怎么解决我的问题，谢谢。