Limiting systems buffers

[Yong Huang]

> Is there a sysctl parameter that will limit the amount of memory
> the kernel uses for systems buffers used for file systems and direct 
>  I/O to a block device?

(While waiting for expert advice...) I think you can lower 
/proc/sys/vm/pagecache and swappiness. But I heard pagecache may not 
work in newer kernels.

The real problem is, applications make memory dirty, unnecessarily. Let's 
say I copy a big file, or gzip it. Lots of memory pages will become 
dirty and they'll be written to disk. If the application (cp, gzip, or 
your Storix) can open files with O_DIRECT option, then the filesystem 
page cache won't be used. 

Otherwise, we could use a filesystem that allows direct I/O mount option. 
I know ext2 or ext3 doesn't support it. (Linus doesn't like the idea.)

Yong Huang