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when cached over 7-8G,the CPU is slowest ,must reboot

Posted: 2007/10/28 03:21:31
by fish01
I am use CentOS 1years ago,it's working fine.

but,last week(2007.10.17),I find,when the cached over 7--8G,the CPU is slowest :

in normal,the cached memory is 5-6G
free memory 2-3G
cpu 1-10%,2-3%sy,90-99%ni,0.1si

when I backup files(1500files,about 4G,copy to another dir),the cached begin increase,when the cached over 7--8G,the CPU is begin slow,cpu 60-80%,20-30%sy, 0%id,0%wa,0.1%hi,13%si,free memory 1.5G
when copy end,the cpu just 90%,in this time,we can not find any ps over 2%,I don't know the Cpu what to do in this time.

service httpd stop
the cpu 0%

service httpd start
the cpu 90%

now,must reboot the system,

my server:

xeon 2x3.2G Nocona
supermicro X6DH8-XB
RAM 10G (1G/6pcs+2G/2pcs)

only run apache&php:

Apache/2.0.52 (CentOS)
PHP Version 4.3.9

Centos x86-64
tried above


when cached over 7-8G,the CPU is slowest ,must reboot

Posted: 2007/10/29 18:14:50
by pjwelsh
My initial thought is this is OK. The system will attempt to cache the disk read *and* the disk writes. The disk writes will begin to take over the system as the cache fills and flushing to *slower* disk must happen. This is when the system "load" gets higher, but the processor(s) are not doing much. Again, this initially looks like normal behavior *until* you rebooted...

As a general rule, you may be better off using "rsync" instead of "cp" for many instances.