Re: Kernel VS application file caching

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

On Jan 21, 2010, at 9:25 AM, Sad Clouds wrote:

> As far as I know Unix kernels will transparently cache files into any 
> available memory to speed up future I/O on those files.
> 
> For applications like Internet servers, which serve many static files from 
> disk, is there any point in implementing file caching at application level? 
> It 
> seems like you would end up with 2 copies of the same data - one copy cached 
> by kernel, another copy cached by application.

To avoid kernel-to-userland copies?

What is your real performance limit?  CPU?  RAM?  I/O bandwidth?  Network 
bandwidth?


                --Steve Bellovin, http://www.cs.columbia.edu/~smb