Re: open(O_DIRECT) on a tmpfs?

[Hugh Dickins <hugh@veritas.com>]

On Thu, 4 Jan 2007, Bill Davidsen wrote:
> 
> In many cases the use of O_DIRECT is purely to avoid impact on cache used by
> other applications. An application which writes a large quantity of data will
> have less impact on other applications by using O_DIRECT, assuming that the
> data will not be read from cache due to application pattern or the data being
> much larger than physical memory.

I see that as a good argument _not_ to allow O_DIRECT on tmpfs,
which inevitably impacts cache, even if O_DIRECT were requested.

But I'd also expect any app requesting O_DIRECT in that way, as a caring
citizen, to fall back to going without O_DIRECT when it's not supported.

Hugh