Firstly I want to say I'm working on no-mmu arch and uClinux.One possibility might be to poke the open method in struct
After much of file operations VFS cache eat up all of the memory.
At this time, if an application request memory which order > 3, the
kernel will report failure.
uClinux use a memory mapped MTD driver to store rootfs, of course it's
in the ram,
So I don't need VFS cache to improve performance. And when order > 3,
__alloc_page() even doesn't try to shrunk cache and slab, just report
failure.
So my thought is remove cache, or limit it. But currently there seems
to be no way in the kernel to do it. So I want to try to use
O_DIRECT. But it seems not to be a right way.