[Qemu-devel] disk cache question and drawback of cache

[longguang.yue]

hi,all

libvirt supply  "default", "none", "writethrough", "writeback", "directsync", "unsafe" disk cache options

 

 

1.

as for qemu,  how qemu uses those options? and  what are the differences?

better  tell me where are the codes corresponding to those options?

 

 

2.

after a long time of running , it seems that vms will slow down?   do you know why? 

cache hit rate goes down or kernel takes time to flush cache?

how to avoid it?

 

 

thanks